feat: allow users to pause prebuilt workspace reconciliation (#18700)

This PR provides two commands:
* `coder prebuilds pause`
* `coder prebuilds resume`

These allow the suspension of all prebuilds activity, intended for use
if prebuilds are misbehaving.

coderd/database/migrations/000345_audit_prebuilds_settings.down.sql

@@ -0,0 +1 @@
+-- No-op, enum values can't be dropped.

coderd/database/migrations/000345_audit_prebuilds_settings.up.sql

@@ -0,0 +1,2 @@
+ALTER TYPE resource_type
+	ADD VALUE IF NOT EXISTS 'prebuilds_settings';