tests: Add a module test integration to hwsim tests

tests: Add a module test integration to hwsim tests

CONFIG_MODULE_TESTS=y build option can now be used to build in module
tests into hostapd and wpa_supplicant binaries. These test cases will be
used to get better testing coverage for various details that are
difficult to test otherwise through the control interface control. A
single control interface command is used to executed these tests within
the hwsim test framework. This commit adds just the new mechanism, but no
module tests are yet integrated into this mechanism.

Signed-off-by: Jouni Malinen <j@w1.fi>