tests/unit: match some unit tests to corresponding feature switches

tests/unit: match some unit tests to corresponding feature switches

Try not to test code that is not used by user mode emulation, or by the
block layer, unless they are being compiled; and fix test-timed-average
which was not compiled with --disable-system --enable-tools.

This is by no means complete, it only touches the more blatantly
wrong cases.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240408155330.522792-5-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>