[Bug][kotlin-spring] add a Spring type converter for enum values #21564

[btpnlsl]

fixes #21564

This PR adds a mustache template file for the Kotlin Spring generator to generate an EnumConverterConfiguration.kt file when the OpenAPI spec has enum or inner enum classes.

By default Spring converts String values to Enum values using the Enum.valueOf method. This won't work for OpenAPI generated enum classes which were done so using a non default enumPropertyNaming setting for the generator.

The Java Spring generator had the same problem in the past and solved it with these PRs: #18259 and #19248

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Kotlin: @dr4ke616 (2018/08) @karismann (2019/03) @Zomzog (2019/04) @andrewemery (2019/10) @4brunu (2019/11) @yutaka0m (2020/03) @stefankoppier (2022/06) @e5l (2024/10)
Issue reporter: @drnta
Java Spring PRs: @martin-mfg @pstorch