What's changed?

Introduces extensibility to the AnnotationTemplateGenerator so that other languages (like Kotlin) can intercept certain steps
Introduced Kotlin specific AnnotationTemplateGenerator so that KotlinTemplate can create valid snippets for annotations

What's your motivation?

AddMockitoExtensionIfAnnotationsUsed currently adds the annotation with a Java style class reference, I'm working on expanding that to work for Kotlin

Any additional context

Without this change a KotlinTemplate like this KotlinTemplate.builder("@ExtendWith(MockitoExtension::class)") will complain about the $ before Class and Placeholder

\607541286333800\openRewriteFile.kt:6:7: error: name expected
class $Clazz {}
      ^
\607541286333800\openRewriteFile.kt:7:1: error: expected annotation identifier after '@'
@interface $Placeholder {}
^
\607541286333800\openRewriteFile.kt:7:12: error: name expected
@interface $Placeholder {}
           ^

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files