remove deprecated createAndExercise and exerciseByKey methods

[S11001001]

Since Daml 2.3.0 #13920, the createAndExercise* and exerciseByKey* methods in Java codegen output are deprecated, with Javadoc explaining how to trivially port to the supported form. After the deprecation cycle is complete, delete the code that generates those methods in TemplateClass (just search for Deprecated or this issue #).

Also consider simplifying ClassGenUtils.generateFlattenedCreateOrExerciseMethod as it will then only have one caller.

• [ ] 15 July 2023 (1 year after 2.3.0)
• [ ] >=Daml 3.0.0