JIT: defer crossgen update when trying to call unboxed entry

[AndyAyersMS]

Some unboxed entries require an additional generic context argument, and
finding the right form for this argument when prejitting is more complex than
it is for jitting. So, defer this update when prejitting.

Resolves #52450.

[AndyAyersMS]

@BruceForstall ptal
cc @dotnet/jit-contrib

Diffs are not as complex as GH default compare makes it seem, try ignoring whitespace: https://github.com/dotnet/runtime/pull/52453/files?diff=split&w=1

[jkotas]

I believe that we have done work to embed this in crossgen2. Is this just a problem for old crossgen?

We should just throw an NYI exception in old crossgen instead of asserting. It is what we have been doing in other similar situations. We are generally not spending time on keeping parity in old crossgen.

[AndyAyersMS]

Yes, it's just a problem for crossgen, and only for a relatively small number of methods.

So I'll revise per your suggestion.

[AndyAyersMS]

Crossgen is already throwing here -- but it is asserting first. So looks like I can just remove the assert.

runtime/src/coreclr/zap/zapinfo.cpp

Lines 1578 to 1582 in 98ac232

	if (IsReadyToRunCompilation())
	{
	_ASSERTE(!"embedClassHandle");
	ThrowHR(E_NOTIMPL);
	}

[AndyAyersMS]

Failure is known: #52464

[AndyAyersMS]

I ran crossgen locally on the two examples with asserts, so don't see the need to run outerloop here.