Convert impl Condition return signature to Option<bool>

[clux]

To allow taking advantage of ? on Option to allow simpler Condition impls.

    fn is_pod_running() -> impl Condition<Pod> {
        |obj: Option<&Pod>| Some(obj?.status.as_ref()?.phase.as_ref()? == "Running")
    }

This also technically allows for distinguishing between;

• condition definitively does not match the condition
• condition could not check properties on the object

Generally, this is probably not hugely valuable, but it allows us to have a clearer answer rather than to conflate missing with either true or false.

Breaking

This is generally not a breaking change. The matches_object fn retains its original signature + behavior. It does this by using the new trait method matches with unwrap_or_default:

    fn matches_object(&self, obj: Option<&K>) -> bool {
        self.matches(obj).unwrap_or_default()
    }

However;

This is a breaking change only for implementors of Condition who now need to return an Option<bool> rather than bool for impl Condition. My thinking is that being able to use option-try makes this worth it. It can be easily communicated that you take the value and put it in a Some otherwise.

This is also a slight breaking change for the newly introduced (#1710) conditions::is_service_loadbalancer_provisioned which was returning true for services the condition did not apply for. Now it returns Some(false) for such services.

[Danil-Grigorev]

Lookup of the conditions is one of the most common scenarios in controller code. If anything can make it simpler, I think it is worth implementing.

[codecov]

Codecov Report

Attention: Patch coverage is 89.74359% with 4 lines in your changes missing coverage. Please review.

Project coverage is 76.0%. Comparing base (57a5e14) to head (e3b341c).

Files with missing lines	Patch %	Lines
kube-runtime/src/wait.rs	88.9%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1498     +/-   ##
=======================================
- Coverage   76.1%   76.0%   -0.0%     
=======================================
  Files         84      84             
  Lines       7859    7843     -16     
=======================================
- Hits        5976    5960     -16     
  Misses      1883    1883             

Files with missing lines	Coverage Δ
kube/src/lib.rs	89.0% <100.0%> (+0.5%)	⬆️
kube-runtime/src/wait.rs	92.1% <88.9%> (-1.3%)	⬇️

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[clux]

I have revamped this after seeing new verbose Condition impls, and thinking this is probably worth it with some care. Now doing it with quite minimal set of breaking changes. Have updated the PR body with details.