[BUG] Scala templates use different case styles and formatters for variables

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
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Description

UPPERCASE value was handled by most of scala templates with do not modify option, but behaviour was different for akka template where output was uPPERCASE

This behaviour become generic and UPPERCASE variables skipped for formatting rules

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractScalaCodegen.java#L172

But regarding to https://docs.scala-lang.org/style/naming-conventions.html only camelCase allowed.

Correct way is to convert UPPERCASE into lowercase and keep naming convention in AbstractScala common to all Scala based templates

openapi-generator version

4.3.0-SNAPSHOT

Related issues/PRs

Start in modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractScalaCodegen.java around line 172, then compare the naming behavior of the Scala templates, especially akka. Confirm the handling described in the issue and the related PR discussion. Done means UPPERCASE variables become lowercase and other variables are camelized consistently across Scala templates.