[FL-1991] Rewrite flash driver (#813)

* Toolbox: fix null pointer dereference in manchester decoder.
* FuriHal: use MPU to protect from null pointer dereference, replace flash driver with our own implementation.

firmware/targets/furi-hal-include/furi-hal-bt.h

@@ -23,6 +23,12 @@ extern "C" {
  */
 void furi_hal_bt_init();
 
+/** Lock core2 state transition */
+void furi_hal_bt_lock_core2();
+
+/** Lock core2 state transition */
+void furi_hal_bt_unlock_core2();
+
 /** Start 2nd core and BLE stack
  *
  * @return true on success
@@ -103,18 +109,6 @@ void furi_hal_bt_notify_buffer_is_empty();
  */
 bool furi_hal_bt_tx(uint8_t* data, uint16_t size);
 
-/** Lock shared access to flash controller
- *
- * @param[in]  erase_flag  true if erase operation
- */
-void furi_hal_bt_lock_flash(bool erase_flag);
-
-/** Unlock shared access to flash controller
- *
- * @param[in]  erase_flag  true if erase operation
- */
-void furi_hal_bt_unlock_flash(bool erase_flag);
-
 /** Start ble tone tx at given channel and power
  *
  * @param[in]  channel  The channel