Resolves: #1460
Summary:
An 'Extend' CTA on workspace schedule banner is added so that a user can
extend their workspace lease from the UI.
Details:
* feat: putWorkspaceExtension handler
* refactor: TypesGen dflt import in workspace.ts
* feat: defaultWorkspaceExtension util
Impact:
This completes the UI<-->CLI parity epic in an MVP way. Of course, a
future improvement to make is extending by times other than the default
90 minutes.