Add search and replace function to coder

[JonasHelming]

fixed #14773

What it does

• Add a new function allowing to search and replace content in files. This is more efficient in big files, as the LLM has less to output compared to replacing the full file.
• Add a ContentReplacer to apply Search and Replace tuples including a match strategy ignoring white spaces
• Add an alternative prompt variant to Coder using the new function as an alternative to full file replace. The LLM can choose which function to use

How to test

Switch the prompt of Coder to "coder-search-replace" and try it. Some example prompts:

'@coder Remove the prefix "MCP" from all user message in packages/ai-mcp/src/browser/mcp-command-contribution.ts'

'@coder Do not display a message to the user anymore about the tools in packages/ai-mcp/src/browser/mcp-command-contribution.ts'

'@coder Allow the user to start already started MCP servers again in packages/ai-mcp/src/browser/mcp-command-contribution.ts'

and also try prompts that should trigger the replace still, e.g.:

'@coder Implement the interface MCPServerManager in the same file (packages/ai-mcp/src/common/mcp-server-manager.ts). Don't ask me anything, jut do it.'

Follow-ups

Test the two variants and decide what should be the default.

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[eneufeld]

Looks good to me and works fine.
The only downside is, that I have to explicitly tell the agent to create the change in chunks as it tends to use the replace whole file function for me.