Add documentation warning for Interlocked.Read write access requirement on 32-bit platforms

[Copilot]

This PR adds critical documentation to the Interlocked.Read methods to warn developers about a non-intuitive behavior that can cause crashes.

Problem

The Interlocked.Read method takes a readonly reference parameter (in parameter), which suggests it only needs read access to the memory location. However, on 32-bit platforms, the method internally uses CompareExchange to ensure atomicity, which requires write access to the memory location.

This causes AccessViolationException when developers attempt to use Interlocked.Read with read-only memory, such as memory-mapped files opened with read-only access:

// This crashes on 32-bit platforms despite appearing safe
using var memoryMappedFile = MemoryMappedFile.CreateOrOpen("TestFile", 100, MemoryMappedFileAccess.Read);
using var accessor = memoryMappedFile.CreateViewAccessor(0, 0, MemoryMappedFileAccess.Read);

unsafe ref readonly long firstLong = ref GetReadOnlyReference(accessor);
long value = Interlocked.Read(in firstLong); // AccessViolationException!

Solution

Added important documentation warnings to both Interlocked.Read(ref long) and Interlocked.Read(ref ulong) methods that clearly explain:

1. Despite taking a readonly reference parameter, the method requires write access on 32-bit platforms
2. This is due to internal use of CompareExchange for atomicity
3. Using it with read-only memory can result in AccessViolationException
4. The issue specifically affects 32-bit platforms only

The documentation uses a prominent [!IMPORTANT] callout to ensure this critical limitation is highly visible to developers.

Impact

This change helps prevent runtime crashes by making developers aware of this limitation upfront, allowing them to choose alternative approaches when working with read-only memory on 32-bit platforms.

Fixes #11658.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[jkotas]

LGTM