Ensure OS functions always report to NMT

os::map_memory_to_file function does not report to NMT[1].

As suggested in [2], violation of convention below may contribute to this and similar problems.
> all os::<memory> functions should report to NMT, and if you don't want that you'd use pd_<memory> functions

A really close issue is that os_posix and os_windows memory functions not always use pd_ convention.

[1] https://github.com/openjdk/jdk/blob/b4984336319adf8762f9812e28fb7f1ddecaee56/src/hotspot/os/posix/os_posix.cpp#L262
[2] https://github.com/openjdk/jdk/pull/812#discussion_r511811348