Consolidate some jit64 tests into less assemblies

[jkoritzinsky]

Reduces the number of project files in the src/tests tree by 4.3% (removes 455 projects).

Part of the continuing effort to get us to a point where we don't need separate inner test builds and the cost of building src/tests multiple times is less than the cost of marshalling the bits from different jobs.

[Copilot]

Pull Request Overview

This PR consolidates multiple JIT64 test projects into fewer assemblies to reduce build overhead. Rather than having each test as a separate project, related tests are grouped together into single assemblies. This effort reduces the project count by 4.3% (removing 455 projects), which helps optimize build times by reducing the cost of building the test tree multiple times and minimizes bit marshalling between jobs.

• Test consolidation via namespace separation instead of separate projects
• Addition of [OuterLoop] attributes to longer-running tests
• Replacement of GCStressIncompatible project properties with [SkipOnCoreClr] attributes
• Refactoring of platform-specific test filtering from runtime checks to attributes

Reviewed Changes

Copilot reviewed 300 out of 957 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
box-unbox*.cs	Added file-scoped namespaces and [OuterLoop] attributes to nullable box/unbox tests
box-unbox*.csproj	Removed individual project files as tests are now consolidated
overflow*.cs	Created individual test files for overflow operations (add, sub, mul, div) with proper namespaces
overflow*.csproj	Removed individual project files and created single rtchecks.csproj
rtchecks.csproj	New consolidated project file listing all overflow test sources
VolatileTest*.cs	Created individual test files for each volatile operator test with namespaces
VolatileTest*.csproj	Removed individual projects; tests now consolidated
VolatileTest.csproj	New consolidated project for all volatile test sources
HugeArray*.cs/csproj	Replaced project-level GCStress settings with test-level [SkipOnCoreClr] attributes
HugeField*.cs/csproj	Replaced project-level GCStress settings with test-level attributes
hugeexpr1.cs/csproj	Added [OuterLoop] and [SkipOnCoreClr] attributes, removed project properties
hugeSimpleExpr1.cs/csproj	Replaced GCStress project properties with [SkipOnCoreClr] attribute
ArrayWithThread.cs/csproj	Moved GCStress configuration from project to [SkipOnCoreClr] attribute
mcc_interop.ilproj	New consolidated project for all mcc interop IL tests
mcc_interop.il	New main entry point that calls all individual mcc test methods
mcc_i*.il	Updated namespaces and replaced runtime platform checks with [PlatformSpecific] or [ConditionalFact] attributes
mcc_i*.ilproj	Removed individual project files as tests are consolidated

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[jkoritzinsky]

/azp run runtime-coreclr outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jkoritzinsky]

/azp run runtime-coreclr outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jkoritzinsky]

/azp run runtime-coreclr outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jkoritzinsky]

/azp run runtime-coreclr outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jkoritzinsky]

/azp run runtime-coreclr outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).