Update default UUID representation to `Standard` (BSON binary subtype 4)

[christophstrobl]

Turn defaulting off and enforce an explicit choice from the user.

[rhanton]

Does this change have a rough ETA out of curiosity? I was surprised that spring-data-mongodb still has this issue when it isn't an issue when using the mongodb driver directly anymore. ☹️

[christophstrobl]

@rhanton thank you for getting in touch. Yes, the defaulting will be changed with the next major release.