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

* Currently toggled by experiment flag

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

coderd/database/dump.sql

@@ -99,7 +99,8 @@ CREATE TYPE resource_type AS ENUM (
     'group',
     'workspace_build',
     'license',
-    'workspace_proxy'
+    'workspace_proxy',
+    'convert_login'
 );
 
 CREATE TYPE startup_script_behavior AS ENUM (