Use unsized delete when we calculate size dynamically in a custom new overload

[jkoritzinsky]

Fixes#119099

[Copilot]

Pull Request Overview

This PR addresses issue #119099 by adding custom operator delete overloads that delegate to unsized delete operators in classes that use dynamically calculated sizes in their custom new operators. This ensures proper cleanup when objects are destroyed, avoiding potential undefined behavior from relying on sized delete with incorrect size values.

Key changes:

• Added custom sized operator delete overloads that call unsized ::operator delete
• Applied this pattern consistently across three classes with dynamic size allocation

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/coreclr/vm/virtualcallstub.h	Added sized delete operator to FastTable class that delegates to unsized delete
src/coreclr/vm/methodtable.h	Added sized delete operator to MethodDataObject class that delegates to unsized delete
src/coreclr/vm/crossloaderallocatorhash.h	Added sized delete operator to KeyValueStore class that delegates to unsized delete

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[AaronRobinsonMSFT]