Sensors API

[thejpster]

We should report sensor info, up to 255 of them. Just like the other APIs.

Neotron Pico BIOS can provide:

• CPU temp (RP2040 on-die reading)
• 5.0V and 3.3V rail voltage (from BMC)
• perhaps some info from the RP2040 bus matrix (bus collisions, etc)
• ROM and die revision

Each value should be of an enum representing the units, and which holds a u32 or similar. This type can then impl Display for printing.

Kind::Voltage(u32) might print as xx.yyy V and be stored in units of 1/1000 Volt.

Kind::Temperature(u32) prints xx.y °C but is stored in units of 1/100 Kelvin.

Kind::RawHex(u32) prints 0xXXXXXXXX

Kind::Percent(u8) prints as xxx %

etc

Each sensor also has a human readable name.