The goal here is to remove a transitive dependency on the deprecated
`atty` crate, which trips `cargo deny` because it's unmaintained.

This currently does not eliminate the dependency completely, as we're
still waiting on `color-eyre` to release [1], and merging this PR as-is
would result in `cargo deny` being even more angry at using different
versions of the same crate, so this PR is a draft for now.

The update is non-trivial because `owo-colors` no longer supports
checking whether stdin supports colors, which is, well, reasonable.

Semantically, this cements the `Stream` trait as something that can be
printed onto, rather than a generic-purpose stream. Uses of `as_tty` are
replaced with a direct call to the `std` `is_terminal` function, and
`Stream` (now called `OwoStream`) now exclusively handles mapping `std`
I/O streams to `owo-colors` streams.

[1]: eyre-rs/eyre#215

The `adler` crate is now deprecated. The recommended replacement is
`adler2`: https://rustsec.org/advisories/RUSTSEC-2025-0056

Update the minimal set of crates in order to remove adler, get adler2,
and have one version of owo-colors.