[FL-3627, FL-3628, FL-3631] fbt: glob & git improvements (#3151)

* fbt: optional shallow submodule checkout
* fbt: more git threads by default
* fbt: git condition fix
* fbt: renamed FBT_SHALLOW to FBT_GIT_SUBMODULE_SHALLOW
* github: enabled   FBT_GIT_SUBMODULE_SHALLOW in flows
* fbt: always compile icons' .c, even if user does not specify a proper source glob; changed glob to require files at user-specified paths to exist
* fbt: fail build for missing imports in .faps
* fbt: moved STRICT_FAP_IMPORT_CHECK to commandline options; enabled by default
* ufbt: enabled STRICT_FAP_IMPORT_CHECK

Co-authored-by: あく <alleteam@gmail.com>

scripts/fbt/appmanifest.py

@@ -100,6 +100,10 @@ class FlipperApplication:
     def is_default_deployable(self):
         return self.apptype != FlipperAppType.DEBUG and self.fap_category != "Examples"
 
+    @property
+    def do_strict_import_checks(self):
+        return self.apptype != FlipperAppType.PLUGIN
+
     def __post_init__(self):
         if self.apptype == FlipperAppType.PLUGIN:
             self.stack_size = 0