OSS WebUI Support for Async Commit/Merge WebUI implementation

[Annaseli]

Closes #9781

Change Description

This PR adds the plugin to implement the WebUI client logic for using the async commit and merge functionality in Enterprise.

Testing

Added a Playwright test.

The Enterprise PR that implements the functionality is here.

[itaigilo]

Nice and clean plugin implementation!

I think that the plugin should be split (see comment in PluginCommitMergeStrategy) though.

[itaigilo]

I think it's much better to handle this in the implementation itself (and avoid checking this here).
Same goes for message.

[itaigilo]

Since these are always false, I think they should better be removed.

[itaigilo]

In the OSS world, commit and merge are not related -
Other than the fact that they both have an async option.
Hence, let's split this into a commit plugin and a merge plugin -
It will require very little extra code.

In addition, the terminology isn't right:
The plugin doesn't provide the "strategy" (for some other component to use), but an actual implementation.

There might be better naming suggestions than the following, but I suggest:

export interface PluginCommitAction {
  run(): Promise<CommitResult>;
}

export interface PluginMergeAction {
  run(): Promise<MergeResult>;
}

[itaigilo]

Looking good, nicely done!

Only Esti fixes, and you should be good to go.

[Annaseli]

@itaigilo
Can you review only the last commit? Added params docs for ts purpose (in a js index file can't declare the params types and without it I have ts errors)

[itaigilo]

@itaigilo Can you review only the last commit? Added params docs for ts purpose (in a js index file can't declare the params types and without it I have ts errors)

Talked on Slack, all good on my side.