Task: Memory Optimisation

[adamfowleruk]

Follow the guide for the wearable sample as per:-

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/app_memory.html#app-memory

• [x] Remove old devices from BLEDatabase after time exceeded
• [x] Remove unused low-level connections from BLEReceiver on Zephyr
• [x] Add max simultaneous connection support to BLECoordinator
• [x] Ensure Zephyr connections are being properly released (so connections are not starved)
• [x] Make max simultaneous tracked devices fixed at compile time in BLEDatabase
• [x] Add optimisation for almost-starved tracking devices (remove oldest)
• [x] Add remove remote initiated connections optimisation (for iOS clients)