qapi: make most CPU commands unconditionally available

qapi: make most CPU commands unconditionally available

This removes the TARGET_* conditions from all the CPU commands
that are conceptually target independent. Top level stubs are
provided to cope with targets which do not currently implement
all of the commands. Adjust the doc comments accordingly.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-ID: <20250522190542.588267-10-pierrick.bouvier@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>