App Suite ImageConverter

SCR-1557

Summary: Removal of remoteCache.enabled flag in Helm chart values, making CacheService usage depending on availability of CacheService and/or via explicit setting of url

Making CacheService usage in clients depending on CacheService availability (global.core-cacheservice.enabled=true) within cluster. In addition, allow to specify external URL for CacheService and allow to disable usage of CacheService via setting blank URL (explicitly: "" value).

To specify for ImageConverter server:

core-imageconverter:
  ## -- Configuration for ImageConverter
  imageconverter:
    cache:
      remoteCache: {}
        # url: https://optional-cache-host:8001/cache or blank (explicitly: "" value) to disable usage of CacheService in case global.core-cacheservice.enabled=true