This PR accounts for further subtleties in `Decimal` parsing:
- Strings which are empty modulo underscores and surrounding whitespace
are skipped
- `Decimal("-0")` is skipped
- `Decimal("{integer literal that is longer than 640 digits}")` are
skipped (see linked issue for explanation)
NB: The snapshot did not need to be updated since the new test cases are
"Ok" instances and added below the diff.
Closes#14204
b8dc780bdc