[FLINK-38517] Fixed equal check to happen after inplace modifications diffResult

[drossos]

What is the purpose of the change

Addresses bug when we include additional podTemplate specs, i.e "Ignored Fields" (using ReflectiveDiffBuilder.clearIgnoredFields()) in the template spec of the FlinkBlueGreenDeployment where it will never come to a conclusion / reconciled state during a Blue-Green deployment.

Brief change log

• *Reordered where we obtain the DiffResult, that strips ignored fields, to occur before the equality check between target and current spec *

Verifying this change

This change added tests and can be verified as follows:
Newly added tests for checking all 3 cases of podTemplate ignored fields:

• testIgnoreForRootPodTemplateAdditionalProps
• testIgnoreForJobManagerPodTemplateAdditionalProps
• testIgnoreForTaskManagerPodTemplateAdditionalProps

Also tested on remote K8 cluster and locally on MiniKube cluster by using a FlinkBlueGreenDeployment spec that contained valid podTemplate fields at the three previously mentioned levels.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changes to the CustomResourceDescriptors: no
• Core observer or reconciler logic that is regularly executed: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? n/a

[ryanvanhuuksloot]

Functionality wise, looks good to me

[ryanvanhuuksloot]

NIT comment lingering, I think we should keep the comment but it needs to move