This PR enables scrolling horizontally in the tab bar.

Currently this requires holding down <kbd>Shift</kbd> for the scroll to
activate. We'll need to look into this.

Scrolling also currently works when there is a split in the editor, as
the non-split view goes down a different rendering path that does not
constrain the pane width, which breaks a number of things.

Release Notes:

- N/A

This PR extracts a new `TabBar` component from the tab bar
implementation in the workspace.

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Wrap width is already assigned from within draw. It can be called
multiple times as taffy iteratively computes the layout.

This fixes a hang we were seeing in nightly when opening the chat panel.

Wrap width is already assigned from within draw. It can be called multiple
times as taffy iteratively computes the layout.

Co-authored-by: Nathan <nathan@zed.dev>

Release Notes:

- N/A

@as-cii and @SomeoneToIgnore noticed a bug where Zed nightly would
continuously report that an update was available. This nightly
auto-update logic depends on the `ZED_COMMIT_SHA` constant, which is
compiled into the app via an rustc environment variable that is assigned
in the `zed2` build script.

I think the bug was caused by the `zed2` build script's output being
cached on our CI, when building the nightly app bundle. The result was
that the `publish-nightly` action updated the "current SHA" for nightly,
but uploaded an artifact whose `ZED_COMMIT_SHA` was cached from an
earlier version.

I've added a line to the `build.rs` that triggers a rerun if the
`.git/logs/HEAD` file has been changed. I think this should prevent the
unwanted caching.

Somehow a condition got inverted and caused the bug.

We're not using these anymore.

Co-Authored-By: Antonio Scandurra <antonio@zed.dev>

We were registering `deploy` only on editors, which did succeed for
channel notes; however, channel note does not have an associated
workspace (that we pulled from the editor). It made more sense to just
register these actions for a workspace, notwithstanding the editor.

This PR also fixes a bunch of cx.dispatch_action calls to call the
handler directly instead (e.g. instead of dispatching ReplaceNext we
just call buffer_search_bar.replace_next instead) as otherwise these
actions are not handled if the buffer search bar does not have the
focus.

Release Notes:

- N/A

This PR fixes an issues where it was possible for panes to overflow the
window (for instance, by having a large number of tabs in the tab bar).

Release Notes:

- N/A

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* Fixed dock toggling not focusing the terminal element
* Fixed loosing focus on dock close (e.g. cmd-d on the last terminal in
the dock)
* Removed element stateless focus API since it would not work when the
element is not rendered, update all API usages to the stateful one via
`gpui::Subscription`

Release Notes:

- N/A

Co-authored-by: Antonio <antonio@zed.dev>

The biggest improvements come from preventing element moves where
unnecessary, and when they are absolutely needed, try to make the struct
we're moving as small as possible. Having big structs on the stack (such
as `Interactivity`) increases the cost of moving but also reduces
opportunities for other compiler optimizations (e.g., inlining).

One more notable change was using `FxHashMap` and `FxHashSet` in hot
code paths where we don't need those collections to be resistant to DoS.

Another thing I am seeing a lot in the profiler is interacting with
`StackingOrder` (cloning it, searching for it, inserting into the
`Scene`). I have some thoughts on how to optimize that but I punted on
it because performance seems to be pretty good now.

Release Notes:

- N/A

Co-authored-by: Antonio <antonio@zed.dev>

Co-authored-by: Antonio <antonio@zed.dev>

Part of
https://linear.app/zed-industries/issue/Z-1386/add-equivalent-setting-to-vscodes-auto-reveal-exclude
Deals with https://github.com/zed-industries/community/issues/800

* add a `project_panel::auto_reveal_entries` config entry to allow
disabling auto reveal in project panel (auto reveal is enabled by
default)
* add a `pane::RevealInProjectPanel` action (and a pane tab context menu
entry) to manually reveal any file entry
* stop auto revealing gitignored directories at all

We can add the auto reveal exclude globs later, if needed, but let's try
to keep the config simpler and start with a more minimalist approach.

Release Notes:

- Improved project panel auto reveal mechanics: gitignored files are not
auto revealed anymore; a `auto_reveal_entries = true` config option for
`project_panel` is added; a `pane::RevealInProjectPanel` action and a
corresponding buffer tab context menu were added

We can also use these maps and sets in place of `SeaHasher` because
they are also deterministic. Note that we're not swapping std's
`HashMap` and `HashSet` wholesale inside of `collections` because
on the server we need cryptographically secure collections.

* gitignored entries are never auto revealed
* `project_panel::auto_reveal_entries = true` settings entry was added,
setting it to `false` will disable the auto reveal
* `pane::RevealInProjectPanel` action was added that activates the project panel and reveals the entry it got triggered on (including the gitignored ones)

Also, fix a bug that prevented drag and drop from working in the collab
panel.

Co-authored-by: Mikayla <mikayla@zed.dev>

This PR is a first pass at styling the welcome screen in Zed2.

Here's the current state:

<img width="1237" alt="Screenshot 2023-12-11 at 7 00 43 PM"
src="https://github.com/zed-industries/zed/assets/1486634/a0cbd5ca-7331-4785-bf46-f83fc4cb3bb6">

Release Notes:

- N/A

- MOAR TESTS

[[PR Description]]

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This PR adds `w_vw` and `h_vh` methods to `StyledExt`.

These methods are the same as their `w` and `h` counterparts, but
operate in viewport units, giving us the equivalent of `vw` and `vh` in
CSS.

You can see them in action in this story:

```
cargo run -p storybook2 -- components/viewport_units
```

Release Notes:

- N/A