Inlined format args make code more readable, and code more compact.
I ran this clippy command to fix most cases, and then cleaned up a few trailing commas and uncaught edge cases.
```
cargo clippy --bins --examples --benches --tests --lib --workspace --fix -- -A clippy::all -W clippy::uninlined_format_args
```
* Fixed leak of `Arc<SharedPool>` in `DecrementSizeGuard::cancel()`
* Renamed `PoolOptions::connect_timeout` to `acquire_timeout` for clarity.
* Fixed `/* SQLx ping */` showing up in Postgres query logs
* Made `.close()` a regular function that returns a `Future`
* Deleted deprecated method `PoolConnection::release()`
* Document why connection might be dropped if `Pool::acquire()` is cancelled
* Added connection metadata to pool lifecycle callbacks
* Improved guarantees for `min_connections`
* Fixed `num_idle()` to not spin forever at high load
* Improved documentation across the `pool` module
