Remove CannotComputeAvailableRangeError import from opentimelineio.core

## Feature Request

Remove the import of ` CannotComputeAvailableRangeError` from the `opentimelineio.core` module.

## Description

This exception is made both available from `opentimelineio.core` and `opentimelineio.exceptions`. I believe it should only be made available from `opentimelineio.exceptions`.

## Context

I discovered this in the context of #1209 and initially removed it there, but @meshula mentioned that it would be a better idea to propose the removal in a separate issue. And after more thinking, I added it back and decided to delay this for another time and create this issue.

Inspect the opentimelineio.core and opentimelineio.exceptions modules to trace where CannotComputeAvailableRangeError is imported and exposed. Remove its exposure from opentimelineio.core while retaining it in opentimelineio.exceptions, then run the relevant API or import tests to confirm both outcomes.

Written by the indexing model from the issue text.