fix(feature): uses server-side apply to reconile

Description

Aligns reconcile strategy for Managed() features to rely on Server-side apply rather than Update. The SSA approach is used by deploy package when reconciling kustomize resources, so keeping it the same makes sense.

The previous one, based on client.Update call, tries to overwrite the entire resource rather than using a patch operation, which can lead to errors when trying to overwrite immutable fields such as:

failed to update object test-namespace/knative-local-gateway: Service "knative-local-gateway" is invalid: [metadata.resourceVersion: Invalid value: "": must be specified for an update, spec.clusterIP: Invalid value: "": field is immutable]

Additional changes

if "managed" annotation is present in one of the resources being part of the feature it will be respected
reworked tests to be more self-descriptive. Extracted funcs were adding more hops while reading the code before understanding what was actually happening

How Has This Been Tested?

In make we trust.

Screenshot or short clip

Merge criteria

[x] You have read the contributors guide.
[x] Commit messages are meaningful - have a clear and concise summary and detailed explanation of what was changed and why.
[x] Pull Request contains a description of the solution, a link to the JIRA issue, and to any dependent or related Pull Request.
[x] Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
[x] The developer has manually tested the changes and verified that the changes work

opendatahub-io / opendatahub-operator

fix(feature): uses server-side apply to reconile #1098

Description

Additional changes

How Has This Been Tested?

Screenshot or short clip

Merge criteria