FIX: Make displayIndex usable for PenState

[brice-gros]

Description

Make displayIndex usable for PenState.

Changes made

Use the displayIndex from PenState to get the target display

Testing

Tested on Android 14

Risk

PenState not working on non-Android platform

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 %%). 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.

[unity-cla-assistant]

All committers have signed the CLA.

[ekcoh]

Hi @brice-gros and thanks for opening this draft PR. Are you expecting to do more work on it or have you accidentally not marked it ready for review?

[ekcoh]

Changes look good, PR only misses an entry in CHANGELOG.md and needs to be updated based on latest develop

[ekcoh]

Adding QA to PR. Also would recommend testing Pen on other platforms that targeted platform and for various Unity generations.

[Pauliusd01]

I don't have any pen devices, added @stefanunity

[stefanunity]

-I don't have an android with a pen, even less the exact device Brice has
-I tested some pen and touch/pointer input on Windows touch screen and wacom + pen
-nothing bad happened

[ekcoh]

Changes LGTM