fix: NGO CoreCLR compatibility

[NoelStephensUnity]

Purpose of this PR

Resolves the NGO CoreCLR test failures and re-enables every test that was disabled for CoreCLR.

Jira ticket

UUM-149592 - NetworkVariable serialization codegen not generated for some types

• CoreCLR enforces generic constraints on method instantiations and Mono does not. The ILPP-generated NetworkVariableSerializationHelper.InitializeSerialization emitted InitializeEqualityChecker_HashSet<HashSet>, which violates T : IEquatable, so CoreCLR rejected the whole method and every type registered by that assembly fell back to FallbackSerializer.
• Removed the IEquatable constraint from InitializeEqualityChecker_HashSet and EqualityEqualsHashSet.
• NetworkBehaviourILPP now validates every emitted serializer and equality checker call against its generic constraints, and reports a compile error instead of emitting IL that CoreCLR rejects.

UUM-149591 - integration tests fail to start server and client instances

• Mostly a consequence of UUM-149592: player prefabs with NetworkVariables threw during synchronization, so connections never completed.
• PeerDisconnectCallbackTests assumed client ids follow creation order. It now finds the target client by id.

UUM-149595 - DAHost player-prefab fetch throws "An item with the same key has already been added"

• NetworkClientAndPlayerObjectTests never cleared m_ChangedPlayerPrefabs between tests and keyed each fetched prefab on the last client's id. It now clears the dictionary on teardown and keys on the fetching client.

UUM-149597 - unexpected owner write-permission error

• OwnerPermissionHideTests assumed client ids follow creation order. Each object's owner is now chosen by client id.

UUM-150429 - Re-enable com.unity.netcode tests disabled for CoreCLR

• Removed all ENABLE_CORECLR [Explicit] and [UnityCoreClrExplicitDisabled] attributes. Every previously disabled test passes on CoreCLR (833/833), and the full PlayMode (5423 passed, 0 failed) and EditMode (1371 passed) suites pass on a trunk CoreCLR editor.

Changelog

NA

Documentation

• No documentation changes or additions were necessary.

Testing & QA (How your changes can be verified during release Playtest)

Functional Testing

Manual testing :

• Manual testing done

Automated tests:

• Covered by existing automated tests
• Covered by new automated tests

Does the change require QA team to:

• Review automated tests?
• Execute manual tests?
• Provide feedback about the PR?

If any boxes above are checked the QA team will be automatically added as a PR reviewer.

Up-port

No up-port needed.

Backports

No back-port needed.

[u-pr]

⚠️ Some settings were ignored in '.pr_agent.toml (repository root)' repo settings

Check the configuration's TOML syntax, permitted settings, and size limit. See the error below.

---

Error message:
Ignored prohibited settings: github_app.handle_pr_actions. Permitted settings were applied.

Configuration content:

# This is the configuration for the u-pr bot
# https://github.cds.internal.unity3d.com/unity/u-pr
# For configuration of this file:
# https://developer.portal.internal.unity.com/catalog/default/component/u-pr/docs/configuration/automatic_runs/

[github_app]
handle_pr_actions = ['opened', 'ready_for_review']  # PR events that auto-run pr_commands
pr_commands       = ["/harness-review"]             # what runs on those events
reviewer_commands = ["/harness-review"]             # what runs when @u-pr is added as reviewer

[u-pr]

💡 Harness Review

The change removes the unused HashSet equality constraint, validates generated serializer and equality calls, and re-enables CoreCLR tests. I examined the codegen paths, runtime equality behavior, client ID fixes, and test edits and found no actionable issues.

_{Reviewed commit 1892ab2}

_{🤖 Helpful? 👍/👎}

[codecov-github-com]

Codecov Report

All modified and coverable lines are covered by tests ✅

@@              Coverage Diff               @@
##           develop-3.x.x    #4171   +/-   ##
==============================================
  Coverage          78.19%   78.19%           
==============================================
  Files                153      153           
  Lines              26272    26272           
==============================================
  Hits               20544    20544           
  Misses              5728     5728           

Flag	Coverage Δ
NGOv2_project_testproject_ubuntu	76.65% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...kVariable/Serialization/NetworkVariableEquality.cs	90.86% <ø> (ø)
...orkVariable/Serialization/TypedILPPInitializers.cs	0.00% <ø> (ø)

Components	Coverage Δ
com.unity.netcode.gameobjects	78.19% <ø> (ø)

ℹ️ Need help interpreting these results?