[REQ] [SPRING] Improve constructor generations

[jpfinne]

Is your feature request related to a problem? Please describe.

Spring constructor can be improved with better support for Jackson and for JSpecify.

Describe the solution you'd like

The Spring generator can generate 3 types of constructors:

• default empty constructor
• constructor for required fields
• constructor for all arguments

We can improve them by adding the @JsonProperty on the fields of the constructors. It is already done in the RestClient.
Adding the @JsonCreator on the all argument constructor to help jackson.
Fix #22757 when using all argument constructors.
Use JSpecify @NullUnmarked on the default constructor to avoid false alarms from code analysis.

Describe alternatives you've considered

custom templates.
Add full support for JSpecify

Additional context