"Temperature" is a parameter in OpenAI GPT models, to control for
randomess in the generated content. To decrease the probability of
either escaping the markdown blocks and creating invalid code, we
decreased temperature for all Non-Prose files. For Markdown or Plain
Text, in which more creativity may be a good thing, we increase the
temperature to allow for more randomness. Along with this, we ask the
generate inline prompt to include only the code and not markdown blocks,
as it appears that lower temperature may decrease the probability of
introducing random markdown blocks.

Release Notes (Internal Only):
- Decrease temperature for inline assist on code content.

Fix some bugs where ChannelNotes and ChannelChat had old cached channel
instances

(This PR was written 100% by the Inline Assistant)

This PR brings in new components into our ai and assistant crates namely
PromptTemplate and PromptChains. They offer a new way to generate
prompts that allow for a more flexible and dynamic approach than before.

Release Notes:
- Introduced PromptTemplate: an abstract base for individual parts of
the prompt.
- Added PromptChains: manage multiple PromptTemplates, sort them based
on priority and regulate the output size based on tokens.
- Provided new PromptArguments structure to encapsulate arguments needed
for PromptTemplate.
    - Extended repository_context to include PromptCodeSnippet.

Co-authored-by: Piotr <piotr@zed.dev>