Rename, clean up boards/variants (#21655)

* Consolidate variant scripts
* Rename Marlin-local boards
* Simplify variants where possible
* Rename variants
* CHITU_F103 and MEEB_3DP: Maple platform `platformio-build-stm32f1.py` uses the 'board' name, not 'board_build.variant' so folder names match 'board' and not `board_build.variant`.

buildroot/tests/chitu_f103

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+#
+# Build tests for chitu_f103 (STM32F103ZE)
+#
+
+# exit on first failure
+set -e
+
+#
+# Build with the default configurations
+#
+use_example_configs Tronxy/X5SA
+exec_test $1 $2 "Tronxy/X5SA" "$3"
+
+# clean up
+restore_configs