[proposed API][builtins] Theia misses part of proposed API: EditSessionIdentityProvider

[marcdumais-work]

Bug Description:

Or part thereof: workspace.onWillCreateEditSessionIdentity

Discovered while testing locally-built vscode built-in extensions 1.77.0, that resulted in a failed activation for vscode.git.

interesting part of the exception:

2023-05-10T18:47:09.885Z root ERROR [hosted-plugin: 2596234] Activating extension 'Git (built-in)' failed: TypeError: r.workspace.onWillCreateEditSessionIdentity is not a function

It looks like it's using a bit of proposed API: EditSessionIdentityProvider that we do not have yet.

Steps to Reproduce:

Use this extension after unzipping it into your plugins folder:
git-1.77.0.zip

Additional Information

Full exception:

2023-05-10T18:47:09.712Z root INFO [hosted-plugin: 2596234] PLUGIN_HOST(2596234): PluginManagerExtImpl/loadPlugin(/tmp/vscode-unpacked/git-1.77.0.vsix/extension/dist/main)
2023-05-10T18:47:09.885Z root ERROR [hosted-plugin: 2596234] Activating extension 'Git (built-in)' failed: TypeError: r.workspace.onWillCreateEditSessionIdentity is not a function
    at new t.GitEditSessionIdentityProvider (/tmp/vscode-unpacked/git-1.77.0.vsix/extension/dist/main.js:2:1424287)
    at S (/tmp/vscode-unpacked/git-1.77.0.vsix/extension/dist/main.js:2:1467662)
    at async A (/tmp/vscode-unpacked/git-1.77.0.vsix/extension/dist/main.js:2:1469905)
    at async t.activate (/tmp/vscode-unpacked/git-1.77.0.vsix/extension/dist/main.js:2:1470972)
    at async PluginManagerExtImpl.startPlugin (/home/lmcmcds/theia/packages/plugin-ext/lib/plugin/plugin-manager.js:310:34)
    at async /home/lmcmcds/theia/packages/plugin-ext/lib/plugin/plugin-manager.js:219:21

• Operating System:
• Theia Version: