[REQ] Better collection serialization support

Is your feature request related to a problem? Please describe.

Since OAS 3.0, in order to support common ways of serializing simple parameters, style and explode are defined instead of collectionFormat.

On the other hand, we still using collectionFormat: style and explode parameters are mapped to collectionFormat.

https://github.com/OpenAPITools/openapi-generator/blob/7dbda049f09edd40662cfc0d00a3bc6e52b257eb/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java#L3083-L3094

https://github.com/OpenAPITools/openapi-generator/blob/7dbda049f09edd40662cfc0d00a3bc6e52b257eb/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java#L4592-L4609

This can not representate serialization format required in OAS3.

Describe the solution you'd like

In order to make available the serialization format, explode and style parameter values should be assigned to mustache templates, and handle the parameters in each generator.

We need to keep collectionFormat until generators support style and explode.

Additional context

Related PR: https://github.com/OpenAPITools/openapi-generator/pull/3984

Start in modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java at the referenced lines, and review the related PR 3984. Trace how style and explode are currently mapped to collectionFormat, then inspect the mustache-template handoff and generator-specific handling. Done means OAS3 serialization values are available without removing collectionFormat compatibility.