Release 0.9.0 (#4256)

* refactor: un-track `Cargo.lock`

* chore: prepare release `0.9.0`

* chore: update `rand`, crypto crates

* chore: update `rand`, crypto crates (2)

* chore: revert `-Z direct-minimal-versions`

For context: https://github.com/launchbadge/sqlx/pull/4173#issuecomment-4376742796

* chore: fix new clippy warnings

* fix: compiler errors in tests/sqlite

* fix: compiler errors in tests/postgres

* fix: errors in `axum-social-with-tests`

* fix: errors in Postgres examples, update `examples/x.py`

* fix(sqlite): don't panic if `call_with_result` didn't set an error message

* chore: update CHANGELOG for 0.9.0

* chore: upgrade `etcetera` to `0.11.0`

* chore: document release PR changes

* chore: document `Executor` methods not for general use

* chore: update copyright