[spring] Add an option "additionalNotNullAnnotations" to include additional NotNull annotations

[wing328]

a follow up PR to #22291

also closes #23093 (related to #21951)

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Summary by cubic

Adds a generator option to control adding @NotNull to Spring path variables and request bodies. By default, @NotNull is no longer emitted; turn on additionalNotNullAnnotations to keep it.

• New Features

  • SpringCodegen option: additionalNotNullAnnotations (default false).
  • Templates now conditionally render @NotNull for path and requestBody.
  • Docs updated (Spring, Java Camel); samples regenerated (spring-boot-x-implements-skip enables the option); JDK17 Spring samples workflow globs fixed.

• Migration

  • If you rely on @NotNull for required path variables or request bodies, set additionalNotNullAnnotations: true (e.g., --additional-properties additionalNotNullAnnotations=true or in config YAML).

^{Written for commit 577f3a3. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 204 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.