feat: add new workspace:share action type (#20198)

Closes
[coder/internal#1012](https://github.com/coder/internal/issues/1012)

coderd/database/migrations/000384_add_workspace_share_scope.down.sql

@@ -0,0 +1,3 @@
+-- No-op: keep enum values to avoid dependency churn.
+-- If strict removal is required, create a new enum type without these values,
+-- cast columns, drop the old type, and rename.

coderd/database/migrations/000384_add_workspace_share_scope.up.sql

@@ -0,0 +1,2 @@
+ALTER TYPE api_key_scope ADD VALUE IF NOT EXISTS 'workspace:share';
+ALTER TYPE api_key_scope ADD VALUE IF NOT EXISTS 'workspace_dormant:share';