Add "Find my phone" app.

[vchigrin]

This change set adds implementation of client for BLE "Immediate alert service", allowing companion apps get notifications from PineTime watch when requested by user.

Fixes: #343

[vchigrin]

This pull request is result of joint work of @jmlich and @vchigrin, most of the code is written by Jozef (personal contributions can be found by commit history).

[vchigrin]

That is how that app looks like

After user presses "Mild" or "High" button phone starts ringing and vibrating. User can stop this either by pressing "None" button on the PineTime, or by pressing button in GadgetBridge companion app on the phone.

To make this work some changes in GadgetBridge application were required, I suppose to upstream this after ensuring that this functionality will be accepted in InfiniTime.

[github-actions]

Build size and comparison to main:

Section	Size	Difference
text	379080B	1584B
data	940B	0B
bss	62660B	-880B

[vchigrin]

Corresponding PR to GadgetBridge
https://codeberg.org/Freeyourgadget/Gadgetbridge/pulls/3746

[NitroNils]

And reverse? Find my watch? Make PineTime blink display and vibrate?
Don't know what this would take. Just a logical follow up 😁

[jmlich]

Find my watch already works. It is Alert Notification Service. In Amazfish -> Settings -> Debug page -> Phone Call.
Also Immediate Alert Service is implemented and shows None/Mild/High levels, but this is not right to find watch.

[crazycrystals]

Sorry if its offtopic, but is it also possible to have something like a signal strength indicator so you can see how close the device is and triangulate it?
Doing a ring with an app could be broken by do not disturb.

[jmlich]

The signal strength or more precisely RSSI (Received Signal Strength Indication) is specified/measured in BLE and Nimble can provide the value. I am not sure if it is reasonable reachable in the code.