feat(coderd): connect dbcrypt package implementation (#9523)

See also: https://github.com/coder/coder/pull/9522

- Adds commands `server dbcrypt {rotate,decrypt,delete}` to re-encrypt, decrypt, or delete encrypted data, respectively.
- Plumbs through dbcrypt in enterprise/coderd (including unit tests).
- Adds documentation in admin/encryption.md.

This enables dbcrypt by default, but the feature is soft-enforced on supplying external token encryption keys. Without specifying any keys, encryption/decryption is a no-op.

docs/api/general.md

@@ -212,6 +212,7 @@ curl -X GET http://coder-server:8080/api/v2/deployment/config \
     },
     "enable_terraform_debug_mode": true,
     "experiments": ["string"],
+    "external_token_encryption_keys": ["string"],
     "git_auth": {
       "value": [
         {