Allow using different models together

Because the class-level properties of `AccelRange` and `GyroRange` are defined when the ICM20948 and ICM20649 are inited, the values overwrite each other if you use both in the same code. The values differ between both models (eg: RANGE_4G is 0 on ICM20649 and 1 on the other), and which values are allowed varies too. One solution would be to have them defined globally with all the values and have each model have its own translation table of allowed values. That would still allow using `AccelRange.RANGE_4G` in user code.
While an edge case, it was reported on discord.

Start by tracing where AccelRange and GyroRange are defined and initialized for ICM20948 and ICM20649. Compare the model-specific allowed values and translations, then verify that both models can be used in the same program while preserving the public AccelRange.RANGE_4G form.

Written by the indexing model from the issue text.