feat: add ability for users to convert their password login type to oauth/github login (#8105)

* Currently toggled by experiment flag

---------

Co-authored-by: Bruno Quaresma <bruno@coder.com>

coderd/database/migrations/000132_oauth_convert_audit.down.sql

@@ -0,0 +1 @@
+-- Nothing to do

coderd/database/migrations/000132_oauth_convert_audit.up.sql

@@ -0,0 +1,2 @@
+-- This has to be outside a transaction
+ALTER TYPE resource_type ADD VALUE IF NOT EXISTS 'convert_login';