Rust 1.84.0 was recently released along with some new clippy lints, one
of which is `unnecessary_map_or`. Unfortunately this lint suggests using
`Option::is_some_and` as a fix, but this is only available in Rust
version >= 1.70, while we still have an MSRV of 1.63. So we silence that
lint for now.
We'd still like our lint CI to use stable Rust so that we can benefit from
new lint checks which may be helpful and don't require an MSRV bump, but
sometimes new lints (like in this case) do.
See:
https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_map_orhttps://doc.rust-lang.org/std/option/enum.Option.html#method.is_some_and
`or_default` is generally less readable than writing out the thing
we're writing, as `Default` is opaque but explicit constructors
generally are not. Thus, we ignore the clippy lint (ideally we
could invert it and ban the use of `Default` in the crate entirely
but alas).
