Add allocation fast path for arrays of value type elements outside Windows

Add allocation fast path for arrays of value type elements outside Windows

- A microbenchmark involving byte array allocation was about 200% faster on Windows compared to Linux
- On Windows, using the portable version of the fast path is about 5% slower than using the asm version on the microbenchmark
- On Linux, using the portable fast path improves the microbenchmark perf by 160%
- With the fast path enabled on Linux, the microbenchmark on Windows (with asm fast path) is now about 17% faster than on Linux.

Commit migrated from https://github.com/dotnet/coreclr/commit/e47ea2c24bab1938791d3c31e6a6510f5b254038