Fix usermod library builds

Manage include folders via a second platformio script, fixing builds and
removing all the extra boilerplate from usermod library.json files.

pio-scripts/fixup_usermods.py

@@ -0,0 +1,17 @@
+Import('env')
+
+# Patch up each usermod's include folders to include anything referenced by wled
+# This is because usermods need to include wled.h
+lib_builders = env.GetLibBuilders()
+um_deps = [dep for dep in lib_builders if "/usermods" in dep.src_dir]
+other_deps = [dep for dep in lib_builders if "/usermods" not in dep.src_dir]
+
+for um in um_deps:
+    # Add include paths for all non-usermod dependencies
+    for dep in other_deps:
+        for dir in dep.get_include_dirs():
+            um.env.PrependUnique(CPPPATH=dir)
+    # Add the wled folder to the include path
+    um.env.PrependUnique(CPPPATH=env["PROJECT_SRC_DIR"])
+       
+#raise RuntimeError("debug")