Fix regex parsing logic handling of nested quantifiers

[davidwendt]

Description

Fixes the libcudf regex parsing logic when handling nested fixed quantifiers. The logic handles fixed quantifiers by simple repeating the previous instruction. If the previous item is a group (capture or non-capture) that group may also contain an internal fixed quantifier as well.
Found while working on #16730

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.