[cDAC] Ensure mt created

[rcj1]

Before checking the dict of MTs when not coming directly from a constructed TypeHandle, ensure that the MethodTable is created.

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[Copilot]

Pull request overview

This PR updates the cDAC RuntimeTypeSystem_1 contract implementation to ensure a MethodTable is validated/created/cached before dereferencing _methodTables[...] in code paths that start from a MethodDesc (rather than from an already-constructed TypeHandle). This reduces the chance of runtime failures (e.g., KeyNotFoundException) when querying generic context/metadata-related properties for a method.

Changes:

• Route MethodDesc-based MethodTable lookups through GetOrCreateMethodTable(methodDesc) instead of directly indexing _methodTables[methodDesc.MethodTable].
• Apply this in generic context location evaluation and in the abstract-method metadata check.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs	Ensures MethodTable is created/cached before dereferencing _methodTables when starting from MethodDesc-driven paths.

Copilot's findings

Comments suppressed due to low confidence (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs:1353

• This change fixes a previously possible KeyNotFoundException when GetGenericContextLoc (via RequiresInstArgMethodTable / IsSharedByGenericInstantiations / IsAbstract) is invoked for a MethodDescHandle whose owning MethodTable hasn't been cached yet (e.g., after GetMethodDescHandle without any prior GetTypeHandle). There are existing cDAC unit tests for IRuntimeTypeSystem/MethodDesc behavior, but none appear to cover this regression. Please add a targeted unit test that calls GetMethodDescHandle(...) and then GetGenericContextLoc(...) without pre-caching the MethodTable, and asserts it does not throw and returns the expected GenericContextLoc for the constructed mock MethodTable/method.

        MethodTable mt = GetOrCreateMethodTable(methodDesc);
        if (mt.Flags.IsValueType)
            return true;

        if (mt.Flags.IsInterface && !IsAbstract(methodDesc))
            return true;

• Files reviewed: 1/1 changed files
• Comments generated: 0