Drop Python 3.10 and add 3.15

[MorganBennetDev]

Preemptively opening this issue so it doesn't get forgotten, but it won't be relevant for a few months yet.

Python 3.10 will reach EOL and Python 3.15 will be released in October of this year (2026). We should drop support for 3.10 once it hits EOL and add support for 3.15 once it's released and our dependencies are compatible.