feat(ble): Add option to disable profile auto save

[huber-th]

Add Kconfig option to disable persisting the BLE profile index after every change. This is useful if the user wants to have the same profile connected at startup regardless of which profile was connected last.

Add &bt BT_SAVE command to manually persist the currently active BLE profile, ensuring it is selected as the active profile on startup.

[caksoylar]

LGTM on docs (also sounds like a good improvement).

[huber-th]

Rebase from main to resolve conflicts in bluetooth.md