Enable gitops to create teams with no enroll secrets, or clear enroll secrets for an existing team (#19616)

Enable gitops to create teams with no enroll secrets, or clear enroll
secrets for an existing team
#19332 

`fleetctl apply` also gains this extra functionality. In `fleetctl
apply` secrets will not be change if one of the following:
- secrets is missing from yml
- They are blank in yml, like: `secrets:`
- They are null in yml, like: `secrets: null`

They will only be cleared with `fleetctl apply` if the user explicitly
sets them to an empty array, like:
- `secrets: []`

# 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/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [x] Added/updated tests
- [x] Manual QA for all new/changed functionality

cmd/fleetctl/testdata/expectedGetTeamsYaml.yml

@@ -29,6 +29,7 @@ spec:
         enable_release_device_manually: false
         macos_setup_assistant:
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null

cmd/fleetctl/testdata/macosSetupExpectedTeam1And2Empty.yml

@@ -29,6 +29,7 @@ spec:
         deadline_days: null
         grace_period_days: null
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null
@@ -63,6 +64,7 @@ spec:
         deadline_days: null
         grace_period_days: null
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null

cmd/fleetctl/testdata/macosSetupExpectedTeam1And2Set.yml

@@ -29,6 +29,7 @@ spec:
         deadline_days: null
         grace_period_days: null
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null
@@ -63,6 +64,7 @@ spec:
         deadline_days: null
         grace_period_days: null
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null

cmd/fleetctl/testdata/macosSetupExpectedTeam1Empty.yml

@@ -29,6 +29,7 @@ spec:
       windows_settings:
         custom_settings: null
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null

cmd/fleetctl/testdata/macosSetupExpectedTeam1Set.yml

@@ -28,6 +28,7 @@ spec:
         deadline_days: null
         grace_period_days: null
     scripts: null
+    secrets: null
     software: null
     webhook_settings:
       host_status_webhook: null