Ban saturating_div, to_num, and from_num

[gztensor]

Description

Remove use of saturating_div, to_num, and from_num and replace with their safe (custom) versions: SafeDiv trait, saturating_to_num, and saturating_from_num respectively.

Note for CI: saturating_div, to_num, and from_num should be forbidden (except in tests, tests should be able to panic).

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe): Security update

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules