Keybindings Editor - add column header sorting

[thevrus]

Adds click-to-sort on column headers in the Keyboard Shortcuts editor.

Changes

• Extends the base Table widget with onDidClickColumn event and setSortColumn() API
• All data columns (Command, Keybinding, When, Source) cycle through ascending → descending → default on click
• Sort indicator arrow and aria-sort attribute on the active column header

How to test

1. Open Keyboard Shortcuts (Cmd+K Cmd+S)
2. Click any column header (Command, Keybinding, When, Source)
3. First click sorts ascending (up arrow), second click descending (down arrow), third click resets
4. Verify sort works together with the "Sort by Precedence" toggle and search filtering

[vs-code-engineering]

📬 CODENOTIFY

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

@joaomoreno

Matched files:

• src/vs/base/browser/ui/table/table.css
• src/vs/base/browser/ui/table/table.ts
• src/vs/base/browser/ui/table/tableWidget.ts

@benibenj

Matched files:

• src/vs/base/browser/ui/table/table.css
• src/vs/base/browser/ui/table/table.ts
• src/vs/base/browser/ui/table/tableWidget.ts

@rzhao271

Matched files:

• src/vs/workbench/contrib/preferences/browser/keybindingsEditor.ts