Implement DacDbi cDAC APIs and simplify generic type context APIs

[Copilot]

Implements four DacDbi APIs in the managed cDAC.

cDAC DacDbi implementations

• GetSimpleType — resolves CorElementType to its metadata token + module via _target.Contracts.RuntimeTypeSystem.
• ResolveAssembly — looks up an assembly ref token through the loader contract.
• ResolveExactGenericArgsToken — walks the generic dictionary to recover the exact instantiation token.
• GetGenericArgTokenIndex — mirrors the native three-state result (S_FALSE / *pIndex = 0 / *pIndex = TYPECTXT_ILNUM).

Each implementation is gated by the existing #if DEBUG legacy cross-check pattern.

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[Copilot]

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[max-charlamb]

I just noticed there is a small pre-existing divergence in RequiresInstArg that we should probably fix.

Native MethodDesc::AcquiresInstMethodTableFromThis excludes only non-abstract interface methods (i.e., DIMs):

 return
     IsSharedByGenericInstantiations()  &&
     !HasMethodInstantiation() &&
     !IsStatic() &&
     !GetMethodTable()->IsValueType() &&
     !(GetMethodTable()->IsInterface() && !IsAbstract());

The cDAC's RequiresInstArg drops the !IsAbstract qualifier and returns true for any interface method.
For a shared generic abstract interface method, this PR's GetGenericArgTokenIndex will return *pIndex = TYPECTXT_ILNUM, while native returns *pIndex = 0 (acquires from this).

[rcj1]

I just noticed there is a small pre-existing divergence in RequiresInstArg that we should probably fix.

Native MethodDesc::AcquiresInstMethodTableFromThis excludes only non-abstract interface methods (i.e., DIMs):

 return
     IsSharedByGenericInstantiations()  &&
     !HasMethodInstantiation() &&
     !IsStatic() &&
     !GetMethodTable()->IsValueType() &&
     !(GetMethodTable()->IsInterface() && !IsAbstract());

The cDAC's RequiresInstArg drops the !IsAbstract qualifier and returns true for any interface method. For a shared generic abstract interface method, this PR's GetGenericArgTokenIndex will return *pIndex = TYPECTXT_ILNUM, while native returns *pIndex = 0 (acquires from this).

I saw that too, PR will be up shortly

Edit: Your suggestion on the generics API sounds good, I think I will just take that and incorporate the changes into this PR

[rcj1]

/ba-g timeout