Option to fully respect SSA

[lictw]

I think will be great if Flux will not override fields which no longer belong to its (lost ownership), single expection - kubectl manager name.

Cases:

• Scale 0 some deployments for some time, for ex. while DB restoring/syncing, and return ownership after that to restore desired state.
• HPA when application creates with replicas != 1, so we can not just omit it.

But most important for me personally - I'm working on release platform, which changes and image field, without which the application simply cannot be created, so it must have a default value, and application also start with some default settings in annotations, which also can be changed over-time. These fields are patched via SSA, but Flux return everything back with every reconcilation.

[stefanprodan]

The way we want to support this use-case is by implementing fluxcd/pkg#696