Allow creating untitled buffers and saving them to new files

Implement `select_line` and `split_selection_into_lines`

Include debug symbols in release mode

Call on_focus on the root view when the window is originally created. Test dropping a focused view. Simplify test to avoid relying on emitting events.

Co-Authored-By: Antonio Scandurra <me@as-cii.com>

Fold ranges are exclusive, exactly like the query ranges. So if the end
of a fold coincides with the start of the query range, we shouldn't
report that fold. Analogously, if the start of a fold coincides with the
end of the query range, that fold shouldn't be reported.

Optimize querying folds

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

This allows us to spawn long-running tasks without leaking entities, but it also ensures that if we *do* hold on to a task, that the entity exists until the future or stream complete so that the task doesn't need to return an Option type.

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

This way, if we create and drop a handle during the creation of a view, we don't drop the view before we have a chance to increment its initial reference count.

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

Otherwise, the element never goes away because the view never goes away because the element is holding a strong reference.

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

This required passing a `Context` object to `Summary` and introducing a
new `SeekDimension` trait that allows comparing two dimensions and pass
an additional context object.

This was a pretty bad oversight.

This is possible now that the window doesn't need to own the view. We can create the root view before we create the window.

Instead, store all views in a single top-level map that's keyed by window id and view id. This ensures we'll keep a view alive even if its window is gone, so long as we're holding a handle. This can happen with things like spawned tasks. We don't want to panic during a spawned task after we close the window.

Synchronize `FoldMap` with buffer's contents lazily

WIP: Create and upload application bundle in CI

And restore skipping of rust install if it hasn't changed.