ams: support building unit test programs on windows/linux/macos

ams: update build system to add generic-fallback support

pgl: Reimplement the pgl sysmodule (#896) ...

* pgl: add skeleton folder to stratosphere

* pgl: Add service interface for IShellInterface

* pgl: begin skeletoning shell service, implement two commands.

* pgl: Implement three more commands.

* pgl: implement bool tracking commands

* pgl: Implement TriggerApplicationSnapShotDumper

* pgl: implement InitializeProcessControlTask

* pgl: Implement pgl::srv::Initialize

* pgl: Implement main()

* pgl: Implement (Get)ShellEventObserver

* pgl: implement LaunchProgramFromHost, GetHostContentMetaInfo

* pgl: Implement ProcessControlTask

* settings: fix duplicate object name

* pgl: fix minor bugs in impl