Convert toolbox to Android.bp

This drops the *TOOLS automated logic, though since there are only
three tools now, that seems less important. It would have been possible
to implement that logic in a Go plugin, but that seems like a lot of
overkill to fix a few duplicated entries.

See build/soong/README.md for more information.

Test: mmma system/core/toolbox
Test: List of installed files is the same
Test: input.h-labels.h and tools.h are the same
Change-Id: I9753083c3f689e689e40001b998b39ad20509598