Breaking: Change regex/iregex to use re.search instead of re.match

[glensc]

Description

Change fetchItem's regex and iregex filters to use re.search rather re.match.

This means that the pattern is now matched from anywhere the string, not start of the string:

• https://docs.python.org/3/library/re.html#search-vs-match

The user can specify ^ in their regex if they want to continue to match the start of the string.

See:

• https://github.com/pkkid/python-plexapi/pull/1350#issuecomment-1927772486

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have added or updated the docstring for new or existing methods
• [ ] I have added tests when applicable