[Pkg-rust-maintainers] Bug#1049389: rust-regex: Please update to v1.8.4

[Peter Green]

> Please update to (at least) newer upstream release v1.8.4.

regex 1.8.x bumps the aho-corasick dependency to 1.x, I took a look through
the reverse dependencies.

* elan - debian dependency but no cargo dependency probablly not an issue

* rust-cpp-macros - patch written but package has very little in the way of tests. https://github.com/mystor/rust-cpp/issues/108

* rust-globset- fixed upstream, not semver breaking.

* rust-grep-regex - fixed in upstream git, but not release yet, and doesn't look reasonable to backport https://github.com/BurntSushi/ripgrep/commit/1035f6b1ff502eb5b1a5fc49a79f45971c772d47

* rust-code-analysis - fixed upstream, not released yet, but patch looks pretty minor https://github.com/mozilla/rust-code-analysis/commit/9b7ead60efb153020133deaa9e6a32b40d40a676

* squeekboard - debian dependency but no cargo dependency probablly not an issue

My conclusion is that we need to wait for a new release of grep-regex before moving on this.

1.9.x also adds a dependency on a new version of regex-automata which is
it's own issue.