Added improvements in to_datetime Error reporting message - incorrect field today/now shown in error

[dannyi96]

• closes #47495

Splitting changes from #47597, This PR aims to close the bug #47495

• Changes description

  • For issue #47495- made change in pandas/_libs/tslib.pyx to accept "now" and "today" values. These values are accepted in other areas of parsing ( _parse_today_now in pandas/_libs/tslib.pyx )

• Example of changed error messages

  Code	Old Error ( on 1.4.3 )	New Error
  pd.to_datetime(["today", "yesterday"])	dateutil.parser._parser.ParserError: Unknown string format: today	dateutil.parser._parser.ParserError: Unknown string format: yesterday present at position 1

[dannyi96]

hi @mroeschke, could you please review this change whenever possible ? Above change does the trick, but not sure if anything else needs to be considered here ( in terms of other existing usecases, etc ) Thanks in advance

[mroeschke]

Thanks @dannyi96