tests/avocado: retire the Aarch64 TCG tests from boot_linux.py

tests/avocado: retire the Aarch64 TCG tests from boot_linux.py

The two TCG tests for GICv2 and GICv3 are very heavy weight distros
that take a long time to boot up, especially for an --enable-debug
build. The total code coverage they give is:

  Overall coverage rate:
    lines......: 11.2% (59584 of 530123 lines)
    functions..: 15.0% (7436 of 49443 functions)
    branches...: 6.3% (19273 of 303933 branches)

We already get pretty close to that with the machine_aarch64_virt
tests which only does one full boot (~120s vs ~600s) of alpine. We
expand the kernel+initrd boot (~8s) to test both GICs and also add an
RNG device and a block device to generate a few IRQs and exercise the
storage layer. With that we get to a coverage of:

  Overall coverage rate:
    lines......: 11.0% (58121 of 530123 lines)
    functions..: 14.9% (7343 of 49443 functions)
    branches...: 6.0% (18269 of 303933 branches)

which I feel is close enough given the massive time saving. If we want
to target any more sub-systems we can use lighter weight more directed
tests.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230203181632.2919715-1-alex.bennee@linaro.org
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>