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.

enterprise/cli/testdata/coder_server_dbcrypt_delete_--help.golden

@@ -0,0 +1,15 @@
+Usage: coder server dbcrypt delete [flags]
+
+Delete all encrypted data from the database. THIS IS A DESTRUCTIVE OPERATION.
+
+Aliases: rm
+
+Options
+      --postgres-url string, $CODER_EXTERNAL_TOKEN_ENCRYPTION_POSTGRES_URL
+          The connection URL for the Postgres database.
+
+  -y, --yes bool
+          Bypass prompts.
+
+---
+Run `coder --help` for a list of global options.