Overhaul bootmagic logic to have single entrypoint (#8532)

* Relocate bootmagic logic to have single entrypoint

* Align init of layer state

quantum/bootmagic/bootmagic_lite.c

@@ -0,0 +1,66 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "quantum.h"
+
+/** \brief Reset eeprom
+ *
+ * ...just incase someone wants to only change the eeprom behaviour
+ */
+__attribute__((weak)) void bootmagic_lite_reset_eeprom(void) {
+#if defined(VIA_ENABLE)
+    via_eeprom_reset();
+#else
+    eeconfig_disable();
+#endif
+}
+
+/** \brief The lite version of TMK's bootmagic based on Wilba.
+ *
+ *  100% less potential for accidentally making the keyboard do stupid things.
+ */
+__attribute__((weak)) void bootmagic_lite(void) {
+    // We need multiple scans because debouncing can't be turned off.
+    matrix_scan();
+#if defined(DEBOUNCE) && DEBOUNCE > 0
+    wait_ms(DEBOUNCE * 2);
+#else
+    wait_ms(30);
+#endif
+    matrix_scan();
+
+    // If the configured key (commonly Esc) is held down on power up,
+    // reset the EEPROM valid state and jump to bootloader.
+    // This isn't very generalized, but we need something that doesn't
+    // rely on user's keymaps in firmware or EEPROM.
+    uint8_t row = BOOTMAGIC_LITE_ROW;
+    uint8_t col = BOOTMAGIC_LITE_COLUMN;
+
+#if defined(SPLIT_KEYBOARD) && defined(BOOTMAGIC_LITE_ROW_RIGHT) && defined(BOOTMAGIC_LITE_COLUMN_RIGHT)
+    if (!is_keyboard_left()) {
+        row = BOOTMAGIC_LITE_ROW_RIGHT;
+        col = BOOTMAGIC_LITE_COLUMN_RIGHT;
+    }
+#endif
+
+    if (matrix_get_row(row) & (1 << col)) {
+        bootmagic_lite_reset_eeprom();
+
+        // Jump to bootloader.
+        bootloader_jump();
+    }
+}
+
+void bootmagic(void) { bootmagic_lite(); }