Fix GH-17122: memory leak in regex

Because the subpattern names are persistent, and the fact that the
symbol table destruction is skipped when using fast_shutdown,
this means the ref

Fix GH-17122: memory leak in regex

Because the subpattern names are persistent, and the fact that the
symbol table destruction is skipped when using fast_shutdown,
this means the refcounts will not be updated for the destruction of
the arrays that hold the subpattern name keys.
To solve this, detect this situation and duplicate the strings.

Closes GH-17132.

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