Default interface methods test fixes

[MichalStrehovsky]

• The diamondshape test should work now that Do not devirtualize shared default interface methods #15979 and Catch ambiguous interface method resolution exceptions #15978 are merged.
• Create debug and retail version of diamondshape and sharedgenerics tests so that we have retail coverage. These tests hit issues around devirtualization (that is only active when RyuJIT is optimizing).

[MichalStrehovsky]

@AndyAyersMS PTAL

[AndyAyersMS]

Do you want to fix up the other tests under DefaultInterfaceMethods while you're at it? Looks like they were all set up the same way.

Can you also add the standard header comment to the .cs and .il files?

[MichalStrehovsky]

Do you want to fix up the other tests under DefaultInterfaceMethods while you're at it? Looks like they were all set up the same way.

Do you mean if I want to add a _r and _d variants of the ilproj? These are primarily type system tests and I don't know if the rest exercises anything interesting from the codegen perspective. We do run them with optimizations enabled in some runs though because the fact they're broken with optimizations was caught in automated runs. I'm not a fan of blindly duplicating the number of tests we run, but if you think some of them are interesting for codegen, I can add those.

Can you also add the standard header comment to the .cs and .il files?

Done

[AndyAyersMS]

You don't need to add two (or more) flavors for each of those other tests -- just fix it so the one flavor will always lead to either be debug or optimized jit codegen. Given the issues we've seen it might as well be optimized.

[MichalStrehovsky]

You don't need to add two (or more) flavors for each of those other tests -- just fix it so the one flavor will always lead to either be debug or optimized jit codegen. Given the issues we've seen it might as well be optimized.

If there's not codegen-related reason why we would want to force debug/optimized for these, I would prefer to stay consistent with the other tests under loader/classloader that don't set DebugType either. It appears different rules apply to different parts of the test tree.

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