Move FileAnsii and FileBrx into ohNetCore.

FileAnsii and FileBrx are Os agnostic and should be generally available.
FileBrx is formerly from libplatform, but should be here.

Implementations of IFile::Open() are still Os-specific.
Add rudimentary File API test.
Fix TestFile Read tests, add quick Write test.

Quick Write test as no implementations currently have write support.
Fix Windows build warnings in TestFile.cpp
hudson_build.py / arm_tests is now sensitive to variant.

Debug or Release settings now passed at invocation of AllTests.py
on the remote device.