[Spring] Optimize and omit unnecessary imports on Api in ApiController templates

[daberni]

This change optimizes the import statements of Spring templates to not import types used for Default Interface and Delegate implementations.

Additionally remove redundant additionalProperty with identical logic.

Additionally gets rid of an unnecessary blank line.

@cachescrubber (2022/02) @welshm (2022/02) @MelleD (2022/02) @atextor (2022/02) @manedev79 (2022/02) @javisst (2022/02) @borsch (2022/02) @banlevente (2022/02) @Zomzog (2022/09) @martin-mfg (2023/08)

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[wing328]

thanks for the pr. looks good

let's give it a try

have a nice weekend