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.

cli/server_createadminuser.go

@@ -63,7 +63,7 @@ func (r *RootCmd) newCreateAdminUserCommand() *clibase.Cmd {
 				newUserDBURL = url
 			}
 
-			sqlDB, err := connectToPostgres(ctx, logger, "postgres", newUserDBURL)
+			sqlDB, err := ConnectToPostgres(ctx, logger, "postgres", newUserDBURL)
 			if err != nil {
 				return xerrors.Errorf("connect to postgres: %w", err)
 			}