Revert "[kotlin] fix query parameter encoding"

[wing328]

Reverts #22512

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Summary by cubic

Reverts the Kotlin Spring RestClient query parameter encoding change and restores the previous URI-building logic. This brings back the earlier behavior for how query params are added and encoded in generated clients.

• Bug Fixes
  • Switch back to RestClient.uri(path) with builder.queryParams(LinkedMultiValueMap(...)).build(params) instead of UriComponentsBuilder.encode().buildAndExpand(...).
  • Update the generator template and the echo_api and petstore samples to match.

^{Written for commit 71f1ddb. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files