MNT: improve RegexFindReplace repr (and maybe others)

[tangkong]

Expected Behavior

The repr should be something readable by humans. Other dataclasses (every config / step) are also basically illegible. Maybe it's worth setting up a more readable representation for those too

Current Behavior

Possible Solution

Some custom __repr__ method

Steps to Reproduce (for bugs)

N/A

Context

#246

Your Environment

pcds-5.8.4