Update: Flexible sample rate.

# This module does not have a way to set sample rate manually.

## _DEFAULT_REPORT_INTERVAL sets fixed rate

[_DEFAULT_REPORT_INTERVAL](https://github.com/adafruit/Adafruit_CircuitPython_BNO08x/blob/main/adafruit_bno08x/__init__.py#L118) has fixed sample rate value.

## Need to make _get_feature_enable_report public not private

[ _get_feature_enable_report](https://github.com/adafruit/Adafruit_CircuitPython_BNO08x/blob/main/adafruit_bno08x/__init__.py#L934) set sample rate. I needs to be get_feature_enable_report, so users can set sample rate manually.

Start in adafruit_bno08x/__init__.py at _DEFAULT_REPORT_INTERVAL around line 118 and _get_feature_enable_report around line 934. Trace how the fixed interval is used and what users need to call to set a sample rate; the work is done when manual sample-rate configuration is available through the public method.

Written by the indexing model from the issue text.