workbench: add commands to move editor to start and end

[kheif]

Closes #250054

Description

This PR implements two new commands to improve editor tab management:

• workbench.action.moveEditorToStart: Moves the active editor to the beginning of the group.
• workbench.action.moveEditorToEnd: Moves the active editor to the end of the group.

Verification

1. Open multiple editors in a group.
2. Select an editor in the middle.
3. Open Command Palette (Cmd+Shift+P or Ctrl+Shift+P).
4. Run "Move Editor to Start" -> Verify the tab moves to index 0.
5. Run "Move Editor to End" -> Verify the tab moves to the last index.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@bpasero

Matched files:

• src/vs/workbench/browser/parts/editor/editor.contribution.ts
• src/vs/workbench/browser/parts/editor/editorActions.ts

[Copilot]

Pull request overview

This PR adds two new commands for improved editor tab management within a group: moving the active editor to the beginning or end of the tab order.

Key Changes:

• Adds MoveEditorToStartAction command to move the active editor to index 0
• Adds MoveEditorToEndAction command to move the active editor to the last index
• Both commands are registered and accessible via the Command Palette (F1)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/vs/workbench/browser/parts/editor/editorActions.ts	Implements two new action classes that execute the move editor command with to: 'first' and to: 'last' arguments
src/vs/workbench/browser/parts/editor/editor.contribution.ts	Imports and registers the new actions to make them available in the workbench

[bpasero]

Thanks!