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ARROW-9863: [C++][Parquet] Compile regexes only once

The cost of compiling those regular expressions is apparently non-trivial in some cases (lots of small files?).

Closes #8107 from pitrou/ARROW-9863-cache-regex

Authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>