FIX: Address CI failure in Package validation tests

[timkeo]

Description

An issue with the trunk merge was brought up on this Slack thread. I don't fully understand the problem but made a lucky guess.

Changes made

Changed the d_InputControl.png asset reference from "url" to "resource".
This matches the other asset references within InputActionsEditorStyles.uss and appeared to fix the Package validation test failure.

Proof of fix: https://unity-ci.cds.internal.unity3d.com/project/2354/branch/timke%2Ftrunk-merge-test

NOTE: The fix for Neutron was pushed onto this trunk-merge branch and should (eventually) land to Neutron main. A forward port shouldn't be necessary.

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.
  • FogBugz ticket attached, example ([case %number%](https://issuetracker.unity3d.com/issues/...)).
  • FogBugz is marked as "Resolved" with next release version correctly set.
• 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.

[Pauliusd01]

LGTM, checked the icon in question and it still works fine, albeit a bit blurry. Though that can be looked at later, this even fixes the blockyness I complained about ages ago on higher DPI screens

[ekcoh]

Good catch, LGTM

[timkeo]

Failure for tvOS test is due to an infrastructure issue and unrelated to this PR.