Remove port-specific test directories and excluded tests from
tinytest-codegen, and let it read said information from an external file.
This way tinytest-codegen is not limited to always generate tests for the
`qemu-arm` target.
This allows having port-specific test directory and excluded tests for more
than one QEMU bare-metal target.
The `qemu-arm` port Makefile was modified to work with the generator
changes and a tests profile file was added to said port.
Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
bea6ff82fa