WPS: Make testing operations configurable at runtime

Instead of build time options (CONFIG_WPS_TESTING_EXTRA_CRED and
CONFIG_WPS_EXTENSIBILITY_TESTING), use a single build option
(CONFIG_WPS_TESTING) and runtime configuration of which testing
operations are enabled. This allows a single binary to be used
for various tests.

The runtime configuration can be done through control interface
with wpa_cli/hostapd_cli commands:
Enable extensibility tests:
set wps_version_number 0x57
Disable extensibility tests (WPS2 build):
set wps_version_number 0x20
Enable extra credential tests:
set wps_testing_dummy_cred 1
Disable extra credential tests:
set wps_testing_dummy_cred 0