Move controller internal triggers to a WatchStreamExt module

[clux]

Would you like to work on this feature?

None

What problem are you trying to solve?

Controlling complexity in controller/mod.rs.

The triggers we have currently are:

1. trigger_with
2. trigger_self
3. trigger_self_shared
4. trigger_others
5. trigger_others_shared
6. trigger_owners
7. trigger_owners_shared

with a call-chain that flows [trigger_owners -> trigger_other -> trigger_with] or [trigger_self -> trigger_with], and the for the shared stream cases differ only in stream input (Arc'd for shared <- #1483 (comment)).

These have bad test coverage and put more complex topics into the one same file.

Describe the solution you'd like

A module referenced in WatchStreamExt that can produce the various trigger streams needed by Controller.

That way the concept of owner-ref-trigger-mapping (or whatever shorthand we want to call it) can have a well-documented home.

Maybe these can also have similar constructors for shared / non-shared. But not sure what is best here.

This possibly needs some finalisation on shared streams first #1472 so probably wait with this for now. I am just marking this down to not forget, and will edit it as ready later.

Describe alternatives you've considered

N/A

Documentation, Adoption, Migration Strategy

1. move to new interface
2. deprecate pub triggers after with clear replacements

Target crate for feature

kube-runtime