Refine Jackson 3 constructors to accept only `JsonMapper` instances for JSON

[sdeleuze]

Originally, Jackson 3 JSON converters, codecs et views constructors were taking an ObjectMapper parameters. I did that to be more lenient and ease migration. @wilkinsona suggested it would be cleaner to use strongly typed JsonMapper which extends ObjectMapper, in order to be consistent across formats supported by Jackson (XmlMapper, SmileMapper, CBORMapper) and avoid the confusion created by instances and beans of type ObjectMapper. I agreed with this proposal, it was too late in the M8 cycle so I had to revert it, but I will plan to merge it earlier in the M9 development cycle.

[sdeleuze]

After a discussion with @snicoll, it looks better to target M9 for such change given how late in M8 we are. So I revert this change on main for now.