Add support for change sets via tool functions

[JonasHelming]

fixed #14678

What it does

Introduce a set of tool functions, which allow agents to create file based change sets. Change sets collect changes, an agent wants to conduct, the user can review them and then decide to apply them.
ChangeSets are managed in a service that supports generic operations to apply the changes. This allows to implement various strategies, e.g. replace content or to work with diffs. To support a new strategy, you need to:

• Provide a new ChangeOperation type
• Provide a corresponding ContentChangeApplier (can apply ChangeOperations on content (strings)). ContentChangeApplier can be registered via a contribution point
• Provide a set of tool functions to create the new operation type

The current PR contains a simple strategy to replace files completely.
The PR introduces also a new agent 'coder' that uses the new tool functions.
The PR renames the workspace functions and template to 'workspace-'

How to test

Ask something like this in the chat:

@Coder I want to add a property "autostart" to the mcp server preferences (packages/ai-mcp/src/browser/mcp-preferences.ts).
Then ask to apply the changes.

Follow-ups

• Provide a UI to review and apply the changesets
• The replace content change applier should have a strategy to correct the file ending break (or we improve the corresponding prompt)
• When attaching a UI, we need to clarify how to pass the UUID of the current changeset.
• Extend the replace operation approach with a second function to only replace specific parts of a file (to make it more efficient)
• Add more strategies, e.g. diff-based
• We should rename 'ai-workspace' to 'ai-ide' or something similar.

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

[planger]

Pretty powerful and nicely implemented, thank you! While I didn't test this in detail --- just a few smaller changes --- it actually performed pretty well.

I've added a few suggestions below, but they are all very minor things.

[planger]

I found the file name replace-changeset-functions.ts confusing as it reads like we replace a change set.
While I understand where the replace comes from in this name, I think it isn't so relevant. How about naming this file write-change-to-file-provider.ts (see also my comment below about the name WriteToFileChangeProvider.

[JonasHelming]

I went for 'replace-content-changeset-functions'

[planger]

I think for now I'd move the content of this file into replace-changeset-functions.ts as it is only used here and rather local. Not sure if it is intended to be used outside of the scope of the tool function WriteToFileChangeProvider.

[JonasHelming]

I think both files will grow a bit, at least with a "search and replace" function. Therefore and in the spirit of keeping files small to work with this replace provider, I would keep it separate :-)