Improve removal of dead calls to allocator helpers.

Improve removal of dead calls to allocator helpers.

This change improves detection of allocators with side effects.
Allocators can cause side effects if the allocated object may have a finalizer.
This change adds a pHasSideEffects parameter to getNewHelper JitEE interface
method. It's used by the jit to check for allocator side effects instead of
guessing from helper ids.

Fixes dotnet/coreclr#21530.

Commit migrated from https://github.com/dotnet/coreclr/commit/eea057675de7914af12c6168db0f3bebea35be5b