Upgrade Unity versions used to run tests on CI

[nowsprinting]

No description provided.

[Copilot]

Pull request overview

Updates the Unity versions used by the CI test matrix to keep coverage current, while pinning a specific Unity 6.0 version for Standalone (player) runs.

Changes:

• Bumped the latest_unity_version used for the “latest” CI run from 6000.3.7f1 to 6000.3.8f1.
• Switched the Standalone (player) test run to use 6000.0.63f1 instead of 2022.3.62f3.

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[github-actions]

Code Metrics Report

	master (3bff361)	#186 (7411b19)	+/-
Coverage	80.2%	80.2%	0.0%
Code to Test Ratio	1:1.0	1:1.0	0.0
Test Execution Time	5m47s	5m42s	-5s

Details

  |                     | master (3bff361) | #186 (7411b19) | +/-  |
  |---------------------|------------------|----------------|------|
  | Coverage            |            80.2% |          80.2% | 0.0% |
  |   Files             |               45 |             45 |    0 |
  |   Lines             |             1663 |           1663 |    0 |
  |   Covered           |             1335 |           1335 |    0 |
  | Code to Test Ratio  |            1:1.0 |          1:1.0 |  0.0 |
  |   Code              |             2917 |           2917 |    0 |
  |   Test              |             3077 |           3077 |    0 |
+ | Test Execution Time |            5m47s |          5m42s |  -5s |

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Reported by octocov