(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.