FIX: OnScreenStick leaking when destroyed

[ekcoh]

Description

Relayed original fix by @LukeUnityDev from here: https://github.com/Unity-Technologies/InputSystem/pull/1960/files to make it easier to land.

Changes made

Unregistering handlers on destroy from associated action.

Testing

Please describe the testing already done by you and what testing you request/recommend QA to execute. If you used or created any testing project please link them here too for QA.

Risk

Please describe the potential risks of your changes for the reviewers.

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.

[ritamerkl]

Nice catch!