FIX: ISXB-586 inputsystem sendpointerhovertoparent

[benoitalain]

Description

Jira ticket: https://jira.unity3d.com/browse/ISXB-586 Trunk PR: https://github.cds.internal.unity3d.com/unity/unity/pull/52658

Trunk PR needs to land first before this PR can be tested (and merged).

Changes made

Implements BaseInputModule sendPointerHoverToParent property for InputSystemUIInputModule. Also properly set PointerEventData reentered and fullyExited properties.

Testing

Manually tested the repro project with the fix. Added 6 unit tests (copied from the uGUI StandaloneInputModule-based tests).

Risk

Even though the changes are mostly copying the code from StandaloneInputModule, the changes are a bit interleaved with other new logic that only exists on the InputSystemUIInputModule side. The relation between those two classes is a bit of a mess (very little reuse of methods that have been put there in the spirit of being reused). I can't be entirely sure that this change is risk-free. I've tested the feature to a reasonable level, but I encourage any QA that knows uGUI more deeply to jump in.

Checklist

Before review:

• [ ] Changelog entry added.
  • Explains the change in Changed, Fixed, Added sections.
  • For API change contains an example snippet and/or migration example.
  • JIRA ticket linked, example (case %<ID>%). If it is a private issue, just add the case ID without a link.
  • Jira port for the next release set as "Resolved".
• [ ] Tests added/changed, if applicable.
  • Functional tests Area_CanDoX, Area_CanDoX_EvenIfYIsTheCase, Area_WhenIDoX_AndYHappens_ThisIsTheResult.
  • Performance tests.
  • Integration tests.
• [ ] Docs for new/changed API's.
  • Xmldoc cross references are set correctly.
  • Added explanation how the API works.
  • Usage code examples added.
  • The manual is updated, if needed.

During merge:

• [ ] Commit message for squash-merge is prefixed with one of the list:
  • NEW: ___.
  • FIX: ___.
  • DOCS: ___.
  • CHANGE: ___.
  • RELEASE: 1.1.0-preview.3.

After merge:

• [ ] Create forward/backward port if needed. If you are blocked from creating a forward port now please add a task to ISX-1444.

[benoitalain]

Seems like the new changes need Editor version defines as it throws errors otherwise

I believe all the errors are fixed now.