Deduplicate projection methods and superinterfaces, fix Representation type gen

[jiholee17]

Follow-up to #877 to dedup method names in generated projections and superinterfaces in generated types.

Also explicitly uses the client package for generated *Representation types. It worked correctly before for schema-defined types but external types broke because the representation type generator used String replace with the external package path to import the Representation type which didn't exist.

[iuliiasobolevska]

Notes from in person discussion:

• evaluate if SchemaExtensionsUtils.collectAllFieldDefinitions could be used in ClientApiGenerator
• log a warn when duplicate schema paths are specified

[jiholee17]

Added warning for when redundant schema paths are specified in build.gradle (i.e. one is a descendant of the other). Generator still makes a best effort to dedup in this case. collectAllFieldDefinitions is already used in ClientApiGenerator to consolidate/dedup fields but not the types themselves, which are duplicated when documents are loaded twice. I kept the distinct() and distinctBy() handling in the client/type generator to handle these cases (which shouldn't happen unless the same file is loaded twice).