Add dynamic column to oauth_clients

Related to gitlab-org/gitlab#602404

Related to gitlab-org/gitlab#604546 (closed)

• MR 1 of 3 (this MR)
• MR 2 of 3: !473 (merged) (enforce PKCE for dynamic clients)
• MR 3 of 3: !560 (merged) (register endpoint)

What does this MR do and why?

Adds a dynamic boolean column (only modified on insert) to oauth_clients and carries it through the internal client APIs (storage, the gRPC mirror, and the consent challenge). Storage groundwork for dynamically registered OAuth clients, nothing gates behavior on it yet.

Database Review

• test-with-postgres
• test-with-yugabyte