[EGD-5490] Add BT pairing documentation

Documentation gives a high-level overview of the following procedures:
-scanning
-pairing
-unpairing

[EGD-5965] Add BT-Harness API documentation

Added documentation:
* BT endpoint API
* BT-Harness tests

[EGD-5658] Add eInk CPU frequency hold

While the screen is being redrawn,
we block CPU frequency decreasing

[EGD-5449] Add final prompts windows

Added Dialog windows for "configuration successful"
"no configuration" and "update OS" for Onboarding.
Refactor Dialog window implementation and usage of
DialogMetadata in other applications.

[EGD-6130] Fix update process (stack size, fscopy)

Increase stack size for service-desktop to 8192
Change fs syscall rename() to copy() (rename seems
to fail when moving data across different filesystems)

[EGD-6131] Fix modem startup

Fix modem start issue
due to bug in battery
level check.

[EGD-5902] Phone Modes Windows

Windows for phone modes created.
Offline:FightMode/messages only ServiceCellularApi created.
ConnectionFrequency and DND options settings throught AppSettings.

[EGD-5565] Fix update process on new lf filesystem

These changes are needed for update to work with new
LFS fileystem, also minor bugfixes are included.

[EGD-6112] Fix Service-desktop crashes during DOM dump

service_stack new size  5120;
worker_stack  new size  8704;

[EGD-6037] Fix stack overflow in the EventManager

Fix stack overflow in the event manager

[EGD-6114] Fix bad end of line in Service cellular

CRLF end of line fixed to Unix one

[EGD-5837] Add USB passthrough for tethering

Tethering has to enable / disable the USB passthrough.

[EGD-5952] Changed service stack depths acc. to real usage

Stack depth changed for:
- Application Manager
- Service Bluetooth
- Bluetooth Worker
- Service Eink
- Service GUI
- Application Special Input

[EGD-6100] Add BT device turn off handling

After BT device disconnects (e.g. because of shutdown) Pure is now
aware of this

[EGD-5512] Usb security refactor and devices pairing

Move all security related functionality to single security endpoint
Paired devices can be added to avoid further passcode requests

[EGD-5919] Fix logs from Service: Cellular, Fota

Remove misleading error message(change to debug/info).
Do not trace as error multiple retry. Minimize (to zero)
error logs on cold and hot start of the phone.

[EGD-6074] Add system message and window for BT initialization error

Purpose of added system message is to sent information about bluetooth
initialization result from bluetooth service to application settings.
Added window will print error if initialization fails.
Further integration in service bluetooth is required.

[EGD-6073] Fix text formatting in retry windows

Error message in retry windows was displayed incorrectly.

[EGD-4853] Add Wake up GSM modem on demand

System wakes up Cellular when there is a need to communicate
with the modem, e.g. to handle an outgoing call

[EGD-5969] Add battery charging UI

Battery charging UI modified
according to design