refactore(test): ignore slow tests locally during pre-push, still run them in CI

[MusabYK]

Description

This is a follow up #75

Notes to the reviewers

I group slow but correct/implemented tests under a nested mod slow { .. } block and add #[ignore]. This excludes them from local cargo test runs (just test/pre-push), but CI targets them all using a single filter: cargo test -- --ignored slow::. slow tests should now be added in mod slow{..} block in any file or crate. Also added just test-slow (alias just ts) and just test-all (alias just ta) since slow tests are still real tests someone may want to run before trusting a change.

Changelog notice

Checklists

All Submissions:

• I've signed all my commits
• I followed the conventional commit guidelines
• I ran just p (fmt, clippy and test) before committing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[nymius]

ACK 6d61ce3