A module is part of check-iocs for a platform when it declares the
check-iocs pair, as before. It is now also part of check-iocs when it
overrides check_indicators() and supports at least one command of that
platform.
The rule lives in module_supports_command(). CmdCheckIOCS already uses
that function to pick its modules, so --list-modules and --module follow
it too. Built-in modules are unaffected. check-iocs takes them from
IOS_CHECK_IOCS_MODULES and ANDROID_CHECK_IOCS_MODULES.
A custom module which replaces a built-in module is covered by the same
rule. If it subclasses the module it replaces, it inherits its
check_indicators() and takes over the re-check of the results file. The
"Replacing a built-in module" section of the plugin documentation is
updated to say that.
check-iocs takes its custom modules from load_custom_modules() like every
check-* command and matches result files to modules by slug, so a plugin
module's stored results are re-checked whenever it declares the
check-iocs pair of its platform; nothing asserted it.