Modify esp_bt_gap_set_scan_mode() to be able to set connection modes as well as disco...

Modify esp_bt_gap_set_scan_mode() to be able to set connection modes as well as discoverable modes

The current API is insufficient to allow the users to set different combinations of connection and discoverable mode

Users should be able to choose the device modes independently:
1. Connectable-
  i. Non-connectable mode
  ii. Connectable mode

2. Discoverable-
  i. Non-discoverable mode
  ii. Limited discoverable mode
  iii. General discoverable mode