[cDAC] Move ARM64 Stackwalking to managed code

[max-charlamb]

Ports the ARM64 unwinder to managed code. The cDAC uses this managed version instead of deferring to the runtime native copy.

I'll remove the native linking in a follow-up PR.

[Copilot]

Pull Request Overview

This PR moves ARM64 stackwalking to managed code, updating the unwind logic in ARM64Context and introducing managed lookup tables for unwind codes.

• Calls to the native unwinding routine are replaced with an instance of ARM64Unwinder for improved managed integration.
• New lookup tables, UnwindCodeSizeTable and UnwindCodeInstructionCountTable, are added using modern C# 12 array initialization syntax.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/ARM64Context.cs	Updated the Unwind method to use ARM64Unwinder and added a relevant using directive to support managed code logic.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/ARM64/LookupValues.cs	Introduced new lookup tables for unwind code sizes and instruction counts using modern C# 12 collection initialization syntax.

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[max-charlamb]

/azp run runtime-diagnostics

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[am11]

Should it be placed at src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/ARM64/, next to existing src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/AMD64/ and /X86/?

[am11]

IMO, we can avoid the redundant arch directories by adding:

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Unwinder/

which will contain ARM64Unwinder.cs, AMD64Unwinder.cs, X86Unwinder.cs and so on.

[max-charlamb]

Thanks, I'll fix this