[EGD-6676] PhoneLock handling with ServiceDesktop

Replaced old PhoneLock handler in ServiceDesktop with new
interactions with Application Manager PhoneLockHandler.

[EGD-6615] Fix tethering repeated notification

Repair of repeated tethering notification
after disconnection.

[EGD-6209] Tethering confirmation popup added

Provided a tethering confirmation popup.
The popup shows up once a USB cable is connected to a PC.

[EGD-5834] Fix restore API

Change restore API
backup/restore/update harness tests

[EGD-6259] Turn off usb security

To prevent errors with USB connectivity and charging screens.

[EGD-5783] Revert EGD-5783

Revert "EGD-5783 Exclude empty body from response message"
This reverts commit b64eb0622b6c5e59eeb2161223e793ba4164ceb9.

[EGD-5783] Exclude empty body from response message

Remove body field from response message,
if it contains null. Add 204 and 501 status codes
and use them in proper responses.
204 stands for success but no content, and 501
means endpoint is not implemented.
Additionally some minor fixes.

[EGD-5868] Add access to backup over MTP

This change adds access to backups via MTP
after backup file has been successfuly created.

[EGD-6111] Timers refactored

Deep refactor of system timers.

[EGD-5945] Bluetooth-harness API messages

This PR:
* provides Bluetooth-Harness API messages definition [EGD-5944]
* provides Bluetooth-Harness API messages implementation
* provides Bluetooth-Harness API usage on harness side [EGD-5946]
* provides Bluetooth-Harness tests [EGD-5947]

[EGD-5837] Add USB passthrough for tethering

Tethering has to enable / disable the USB passthrough.

[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-5304] Add new way of system close

Unified method of closing
the system orchestrated by
system manager

[EGD-5326] Fixed AT commands harness utility

We can now use test harness to send and check at commands

[EGD-5757] Fix backup API

Fix backup endpoint to work with new paths and FS api
The flow is based on the design in confluence.

[EGD-5204] Show passcode screen only when PC is connected

USBConfigured event is not fired when powerbank, charger is connected.

[EGD-5204] Show passcode screen only when PC is connected

USBConfigured event is not fired when powerbank, charger is connected.

[EGD-5756] Add Update Window

Create Update Window(s) to control and visualize the MuditaOS update
process on Pure.

[EGD-5204] Secure USB communication

Secure all endpoints by returning 403(Forbidden) when USB is connected.
Request screen passcode to enable secured endpoints.

[EGD-5204] Secure USB communication

Secure all endpoints by returning 403(Forbidden) when USB is connected.
Request screen passcode to enable secured endpoints.

[EGD-5870] Fix filesystem remounting

Skip remounting if a filesystem is already R/W