* rpc: increase RPC buffer size. Add get available buffer size API
* bt: add flow control characteristic to serial service
* ble: change updating flow control characteristic logic
* rpc: add buffer is empty callback
* bt: add notification about empty RPC buffer
* ble: add more debug info
* serial_service: add mutex guarding available buffer size
* ble: remove debug logs in serial service
- RPC: added CLI command to start session - all input bytes goes into RPC, all RPC output goes into VCP
- RPC: added command to close session (actually it only notifies transport layer)
- RPC: added recursive rmdir
- RPC: hard-coded listing for root directory (any, ext, int)
- Fixed CLI leak
- Fixed furi_record_delete leak
- Unit tests: repaired
- Unit tests: corrected output - remove excess, change dots with progress spinner
- Unit tests: added leak check
- Unit tests: SD mount check before start
Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>
