[release/7.0] [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.

[ghost]

Tagging subscribers to this area: @BrzVlad
See info in area-owners.md if you want to be subscribed.

Issue Details

---

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:	area-Codegen-Interpreter-mono
Milestone:	-

[BrzVlad]

From the original PR, this doesn't contain the 846f4ea commit, since it is unnecessary risk for backport PR

[SamMonoRT]

@carlossanlop - this is approved via Tactics email, but we should wait till @BrzVlad confirms the CI failures are not relevant.

[BrzVlad]

I'm not seeing any failures with this

[carlossanlop]

Approved by Tactics (7.0.3).
Signed off by area owner.
CI failure is known/unrelated/already fixed #78778 .
No OOB changes needed.
Ready to merge.