fleetctl gitops (#16535)

Add `fleetctl gitops` command for #13643 

Code review video:
https://www.loom.com/share/7941c51c709b44ccafd618dd05837d99?sid=27b923d7-1393-4396-bac7-30616b2d6de9

fleet-gitops PR that also needs review:
https://github.com/fleetdm/fleet-gitops/pull/26

Working global/team gitops configs that can be used for testing:
https://github.com/fleetdm/fleet-gitops/tree/victor/fixing-configs

# Checklist for submitter

If some of the following don't apply, delete the relevant line.

<!-- Note that API documentation changes are now addressed by the
product design team. -->

- [x] Changes file added for user-visible changes in `changes/` or
`orbit/changes/`.
- [x] Added/updated tests
- [x] Manual QA for all new/changed functionality

pkg/spec/testdata/agent-options.yml

@@ -0,0 +1,14 @@
+command_line_flags:
+  distributed_denylist_duration: 0
+config:
+  decorators:
+    load:
+    - SELECT uuid AS host_uuid FROM system_info;
+    - SELECT hostname AS hostname FROM system_info;
+  options:
+    disable_distributed: false
+    distributed_interval: 10
+    distributed_plugin: tls
+    distributed_tls_max_attempts: 3
+    logger_tls_endpoint: /api/v1/osquery/log
+    pack_delimiter: /