Rename test/hs/test to htest

The current base name of 'test' means that this binary will generate
profiling, coverage, etc. files with the name 'test.*', result in
tab-completion conflicts with the test directory. Let's slightly
change its base name for typing easiness.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>