[compiler-rt] [msan] Increase kNumStackOriginDescrs constant (PR #92838)

[Thurston Dang via llvm-commits]

thurstond wrote:

> Hmm I did not consider the relocation offset. This can realistically push some other .bss variable out of the 2Gb range if the linker is not smart enough to place the largest object last. The 2Gb is not just MSan rtl budget, but for the whole program.
> 
> Lets bring this down to 4M origins, that should be enough for the foreseeable future.

Done!

https://github.com/llvm/llvm-project/pull/92838