Add system setting to mirror bluetooth pairing database to sd card (#1787)

* ams_mitm: add ability to mirror bluetooth device pairing database to sd card via a system setting

* ams_mitm: address requested stylistic changes

* ams_mitm: make use of R_SUCCEED macro

* ams_mitm: use settings::BluetoothDevicesSettings instead of libnx type

* ams_mitm: fix logic error when truncating pairing database on read

* Update .ini comment

* ams_mitm: missing R_TRY around call to fs::FlushFile

* stratosphere: remove union from BluetoothDevicesSettings type

---------

Co-authored-by: ndeadly <24677491+ndeadly@users.noreply.github.com>

config_templates/system_settings.ini

@@ -67,6 +67,10 @@
 ; Note that this setting is ignored (and treated as 1) when htc is enabled.
 ; 0 = Disabled, 1 = Enabled
 ; enable_log_manager = u8!0x0
+; Controls whether the bluetooth pairing database is redirected to the SD card (shared across sysmmc/all emummcs)
+; NOTE: On <13.0.0, the database size was 10 instead of 20; booting pre-13.0.0 will truncate the database.
+; 0 = Disabled, 1 = Enabled
+; enable_external_bluetooth_db = u8!0x0
 [hbloader]
 ; Controls the size of the homebrew heap when running as applet.
 ; If set to zero, all available applet memory is used as heap.