OOTB: make update and host-container systems optional

[webern]

When building my own custom variant of Bottlerocket, I want to be able to opt-out of certain core systems. In particular I want to create a variant that doesn't support in-place updates and doesn't support host containers.

To do this we will need to make sure the rest of Bottlerocket works when these packages are not installed. os.spec may need to be broken up.