enable substituteGenericPagedModel feature also for spring-cloud libraries in java spring and kotlin spring code gens as there is no practical reason to forbid it.

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Summary by cubic

Adds substituteGenericPagedModel support for spring-cloud in both spring and kotlin-spring, removing the prior library restriction and updating docs. When enabled, paginated schemas are replaced with PagedModel<T>, and the original page/pagination models are not generated.

• New Features

  • Respects importMappings.PagedModel; only generates the PagedModel supporting file when no custom mapping is set.

• Bug Fixes

  • CI: retry apt-get installs with exponential backoff to reduce failures from transient network errors.

^{Written for commit 4de69f8. Summary will update on new commits.}