[FLINK-29581] Trigger warning event for session job reconciliation exception

[haoxins]

What is the purpose of the change

Trigger warning event for session job reconciliation exception. Will be useful for monitoring.

Brief change log

Trigger warning event for session job reconciliation exception

Verifying this change

This change is already covered by existing tests, such as (please describe tests).

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)

[haoxins]

Can you please add a test case for this?

will do

[gyfora]

thank you!