target allocator: add configurable mTLS option for TA crds

[Horiodino]

Description:
Added mtls.enabled option to Target Allocator (in both OpenTelemetryCollector and TargetAllocator ). This replaces the operator.targetallocator.mtls feature gate.

Link to tracking Issue(s):

• Resolves: Add a config option for enabling target allocator mTLS #4915

Testing:

• Updated unit tests.
• Updated e2e tests.

Documentation:

• Updated API docs and added changelog.

[swiatekm]

You don't need to add this to v1alpha1, we're going to be removing it shortly.

[github-actions]

E2E Test Results

2 files  6 suites   6m 13s ⏱️
3 tests 3 ✅ 0 💤 0 ❌
6 runs  6 ✅ 0 💤 0 ❌

Results for commit 3ea4361.

♻️ This comment has been updated with latest results.

[Horiodino]

cc @swiatekm

[swiatekm]

You also need to update the documentation in cmd/otel-allocator to reflect this change.

[swiatekm]

I think we need to think about this more carefully. This feature should also work for the TargetAllocator CRD, which I don't believe is the case right now. The way this is typically implemented is that there's an attribute on TargetAllocator.spec, and setting it on the Collector forwards it there in https://github.com/open-telemetry/opentelemetry-operator/blob/main/internal/manifests/collector/targetallocator.go.

In this case, we also need to do some stuff in the Collector itself, and the right check for this is by looking at params.TargetAllocator, the same way this is done for config manipulation. The reverse of what this PR does, where it checks the collector CR while generating the TargetAllocator manifests.

Does that make sense, @Horiodino ?