Fix named mutexes on OSX to work between arm64 and emulated x64 processes (#62765)

Fix named mutexes on OSX to work between arm64 and emulated x64 processes (#62765)

- The page size is different between arm64 processes and emulated x64 processes
- The shared memory file size is set to the page size and there was a strict check on the file size, leading to an exception from the second process of a different arch that tries to share the same mutex
- Made the file size check less strict, and allowed an arch to increase but not decrease the file size such that it can be mapped at page size granularity
- Fix for https://github.com/dotnet/runtime/issues/62140 in main