Naming 'anonymous' mmap memory, which we use for Reactor's executable
memory, enables profilers to attribute JIT-compiled routine execution
to SwiftShader.

Bug: b/174801963
Change-Id: I3b1558fb89d1cac42f65be0609cfa5ac2a8319ef
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/52129Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Jason Macnak <natsu@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>