Update Rust crate regex to 1.9.5

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
regex	dependencies	patch	1.9.4 -> 1.9.5

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Release Notes

rust-lang/regex (regex)

v1.9.5

Compare Source

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This is a patch release that hopefully mostly fixes a performance bug that
occurs when sharing a regex across multiple threads.

Issue #​934
explains this in more detail. It is also noted in the crate
documentation.
The bug can appear when sharing a regex across multiple threads simultaneously,
as might be the case when using a regex from a OnceLock, lazy_static or
similar primitive. Usually high contention only results when using many threads
to execute searches on small haystacks.

One can avoid the contention problem entirely through one of two methods.
The first is to use lower level APIs from regex-automata that require passing
state explicitly, such as meta::Regex::search_with.
The second is to clone a regex and send it to other threads explicitly. This
will not use any additional memory usage compared to sharing the regex. The
only downside of this approach is that it may be less convenient, for example,
it won't work with things like OnceLock or lazy_static or once_cell.

With that said, as of this release, the contention performance problems have
been greatly reduced. This was achieved by changing the free-list so that it
was sharded across threads, and that ensuring each sharded mutex occupies a
single cache line to mitigate false sharing. So while contention may still
impact performance in some cases, it should be a lot better now.

Because of the changes to how the free-list works, please report any issues you
find with this release. That not only includes search time regressions but also
significant regressions in memory usage. Reporting improvements is also welcome
as well! If possible, provide a reproduction.

Bug fixes:

• BUG #​934:
  Fix a performance bug where high contention on a single regex led to massive
  slow downs.

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