[AE-74] Revamp Battery API for Nicla Sense ME

[sebromero]

Change log

🐛 Fixed Bugs

• Fixed the incorrect calculation of the battery voltage percentage.
• Fixed incorrect voltage reading by adding a tiny delay to give the chip time to wake up from High Impedance mode.
• Fixed a slightly incorrect interpretation of the NTC values (introduced a new state 'Extreme' which indicates the charging has been suspended).
• Fix edge case in the charging current setting that could cause an external value to be used instead of a programmatic one.
• Fix incorrect TS and interrupt disable in enableCharging function

🚀 Enhancements

• Added documentation to all functions related to power management.
• Added error handling to catch error cases
• Introduced Enums for battery charge level, temperature and operating status.
• Avoided high impedance mode when connected through VIN to to correctly report charging status
• Improved accuracy of battery voltage reading (disable charging while reading)

🆕 New Features

• Implemented a WebBLE based battery monitor + sketch for easy testing without external power supply
• Remove battery status function and replace with temp and charge level.
• Added function for toggling battery NTC.
• Added API for operating system status (e.g. charging).
• Added API to set regulated battery voltage.
• Added function to determine power source
• Added function to disable charging state