Migrate from isort to ruff

[Cadair]

Describe the feature

The first iteration of the package template kept isort around because sunpy core uses the length_sort_sections config key which ruff doesn’t have support for.

I think we could drop the use of this config option and alphabetically sort everything, but this should be done as a standalone migration as it will generate large diffs to all the repos using the config option currently, especially core.

Proposed solution

No response

[settwi]

how about making a schedule for migration? so core is on day X, then other packages get isort dropped at regular intervals

[Cadair]

I think we can do it in one go using the regular tooling (or the automations will do it anyway!), but we should do it when we have the time to do the work.