sensor: icm45686: Add basic sensor functionality

- Add support for Fetch/Get API.
- Add support for Read/Decode API.
- Add config settings through device-tree.
- Add bus support for SPI (although easily extensible to others as
based on RTIO).

Fetch/Get API tested with accel_polling sample.
Read/Decode API tested with sensor_shell sample.

Signed-off-by: Luis Ubieda <luisf@croxel.com>