applyOptionsForConverter

Applies ParserOptions to get a ParserFunction that can be run in case this StringParser is turned into a converter (like at Parsers.getAsConverterOrNull).

By default, this should do the same as applyOptions but it may be customized. For instance, maybe the parser is skipped due to GlobalParserOptions but this should not happen during conversion.

Or, because we know what the expected parsed type should be, we can enable fallback parsing via an intermediate type that may also be a parse target, such as:

String ->DateTimeComponents ->LocalDate

It's even okay if we lose some information in the process, meaning we can convert "10-04-2026 13:11:42" to LocalDate(2026, 4, 10).

This is different from if we were to just call parse() and be happy if any non-String type comes out.