[Java Libraries] Jakarta Validation API support useJakartaEe flag

[horaceli]

Fixes #19398 and #19437

For context, useJakartaEe previously only determined the javax/jakarta imports for validation-api, not the maven Jakarta dependency version (that only worked for annotation-api).

#18332 and #19171 aligned the validation-api to use jakarta.* package as a previous commit had already upgraded the validation-api version to 3.x. Unfortunately this caused a regression as end users can manually specify 2.x, in which case they would still need the javax.* package. This partially reverts those changes and once again makes the javax/jakarta package configurable.

This PR allows the use of useJakartaEe flag in the same way Jakarta annotation-api switches between javax.* and jakarta.* packages. This also switches between jakarta.validation-api 2 and 3 so the correct dependencies are included.

Note that it only applies to generators in Java/libraries

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