[FL-2859,2838] fbt: improvements for FAPs (#1813)

* fbt: assets builder for apps WIP
* fbt: automatically building private fap assets
* docs: details on how to use image assets
* fbt: renamed fap_assets -> fap_icons
* fbt: support for fap_extbuild field
* docs: info on fap_extbuild
* fbt: added --proxy-env parame ter
* fbt: made firmware_cdb & updater_cdb targets always available
* fbt: renamed fap_icons -> fap_icon_assets
* fbt: deprecated firmware_* target names for faps; new alias is "fap_APPID"
* fbt: changed intermediate file locations for external apps
* fbt: support for fap_private_libs; docs: updates
* restored mbedtls as global lib
* scripts: lint.py: skip "lib" subfolder
* fbt: Sanity checks for building advanced faps as part of fw
* docs: info on fap_private_libs; fbt: optimized *.fam indexing
* fbt: cleanup; samples: added sample_icons app
* fbt: moved example app to applications/examples
* linter fix
* docs: readme fixes
* added applications/examples/application.fam stub
* docs: more info on private libs

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

assets/SConscript

@@ -9,28 +9,13 @@ assetsenv = env.Clone(
 )
 assetsenv.ApplyLibFlags()
 
-if not assetsenv["VERBOSE"]:
-    assetsenv.SetDefault(
-        ICONSCOMSTR="\tICONS\t${TARGET}",
-        PROTOCOMSTR="\tPROTO\t${SOURCE}",
-        DOLPHINCOMSTR="\tDOLPHIN\t${DOLPHIN_RES_TYPE}",
-        RESMANIFESTCOMSTR="\tMANIFEST\t${TARGET}",
-        PBVERCOMSTR="\tPBVER\t${TARGET}",
-    )
-
-# Gathering icons sources
-icons_src = assetsenv.GlobRecursive("*.png", "icons")
-icons_src += assetsenv.GlobRecursive("frame_rate", "icons")
-
-icons = assetsenv.IconBuilder(
-    assetsenv.Dir("compiled"), ICON_SRC_DIR=assetsenv.Dir("#/assets/icons")
+icons = assetsenv.CompileIcons(
+    assetsenv.Dir("compiled"), assetsenv.Dir("#/assets/icons")
 )
-assetsenv.Depends(icons, icons_src)
 assetsenv.Alias("icons", icons)
 
 
 # Protobuf .proto -> .c + .h
-
 proto_src = assetsenv.Glob("protobuf/*.proto", source=True)
 proto_options = assetsenv.Glob("protobuf/*.options", source=True)
 proto = assetsenv.ProtoBuilder(assetsenv.Dir("compiled"), proto_src)