[release/6.0] [mono][interp] Add unbox when calling valuetype method through delegate

[BrzVlad]

If we are calling an open instance delegate, where the target method is on a valuetype, we will need to unbox this pointer.

Backport of #79445

Fixes#79354

Customer Impact

MAUI iOS applications making use of the popular AutoMapper NuGet library can crash in debug builds. Workaround is to disable mono interpreter and implicitly hot reload. Other platforms using interpreter, like blazor wasm, can potentially hit this issue even in Release.

Testing

Verified fix on sample app provided in the bug report and created a simple test case that is included in our suite.

Risk

Low. The fix only touches the code path for a very specific type of delegate invocation pattern which was previously handled incorrectly before.

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Issue Details

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If we are calling an open instance delegate, where the target method is on a valuetype, we will need to unbox this pointer.

Backport of #79445

Fixes #79354

Customer Impact

MAUI iOS applications making use of the popular AutoMapper NuGet library can crash in debug builds. Workaround is to disable mono interpreter and implicitly hot reload. Other platforms using interpreter, like blazor wasm, can potentially hit this issue even in Release.

Testing

Verified fix on sample app provided in the bug report and created a simple test case that is included in our suite.

Risk

Low. The fix only touches the code path for a very specific type of delegate invocation pattern which was previously handled incorrectly before.

Author:	BrzVlad
Assignees:	-
Labels:	Servicing-consider, area-Codegen-Interpreter-mono
Milestone:	-

[SamMonoRT]

/cc @carlossanlop - approved via Tactics email. @BrzVlad - please confirm CI failures are not related. Thanks.

[BrzVlad]

The failures don't look related and I see them also on other PRs so this is good

[carlossanlop]

Approved by Tactics (6.0.14).
Signed off by area owners.
No OOB changes needed.
CI failures investigated as unrelated.
Ready to merge.