scripts: ci: check_compliance: Add sysbuild Kconfig checks

Introduce sysbuild-specific variants of existing Kconfig checks:

  * SysbuildKconfig
  * SysbuildKconfigBasic
  * SysbuildKconfigBasicNoModules

This involves a few additions to the base `KconfigCheck` class:

  * Supporting a variable symbol prefix, to handle `SB_CONFIG_`.
  * Generating extra files, including `Kconfig.sysbuild.modules`.
    Although these are never sourced outside of sysbuild Kconfig,
    they're still generated for every regular Zephyr build, so it's
    natural to let all Kconfig checks follow this behavior.

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>