Use extension everything to polyfill ArgumentNullException.ThrowIfNull

[stephentoub]

cc: @jaredpar, @jcouv, @ericstj

[Copilot]

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src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.NativeAot.cs:92

• ArgumentNullException.ThrowIfNull is being applied to an IntPtr (a value type), which will never be null. If the intent is to validate that 'ptr' is not equal to IntPtr.Zero, consider an explicit check for that condition.

ArgumentNullException.ThrowIfNull(ptr);

src/libraries/Common/src/System/ExceptionPolyfills.cs:12

• [nitpick] Consider adding unit tests to verify the behavior of the new polyfill implementation for ThrowIfNull to ensure it correctly handles various argument types.

extension(ArgumentNullException)

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