This finishes up the rewrite of `update_lints.py` in Rust. More
specifically, this
* adds the `--check` flag and handling to clippy_dev
* tracks file changes over the different calls to `replace_region_in_file`
* only writes changes to files if the `--check` flag is *not* used
* runs `./util/dev update_lints --check` on CI instead of the old script
* replaces usage of the `update_lints.py` script with an error
`./util/dev update_lints` behaves 99% the same as the python script.
The only difference that I'm aware of is an ordering change to
`clippy_lints/src/lib.rs` because underscores seem to be sorted
differently in Rust and in Python.
🏁
The update script now also generates the 'register_removed' section in
`clippy_lints/src/lib.rs`.
Also, instead of using `let mut store ...`, I added a new identifier
line so that the replacement will continue to work in case `let mut
store ...` ever changes.
