fbt: source collection improvements (#3181)

* fbt: reduced amount of redundant compilation units
* fbt: added GatherSources() method which can reject source paths starting with "!" in sources list; optimized apps' source lists
* docs: updated on path exclusion for `sources`
* apps: examples: fixed example_advanced_plugins source list
* docs: more details on `sources`; apps: narrower sources lists

applications/main/subghz/application.fam

@@ -7,6 +7,11 @@ App(
     icon="A_Sub1ghz_14",
     stack_size=3 * 1024,
     order=10,
+    sources=[
+        "*.c",
+        "!subghz_cli.c",
+        "!helpers/subghz_chat.c",
+    ],
     resources="resources",
     fap_libs=["assets", "hwdrivers"],
     fap_icon="icon.png",
@@ -18,5 +23,6 @@ App(
     targets=["f7"],
     apptype=FlipperAppType.STARTUP,
     entry_point="subghz_on_system_start",
+    sources=["subghz_cli.c", "helpers/subghz_chat.c"],
     order=40,
 )