Reorganize BaseService-related modules (#2831)

core/base-service/base-json.js

core/base-service/base-json.spec.js

core/base-service/base-non-memory-caching.js

core/base-service/base-static.js

core/base-service/base-svg-scraping.js

core/base-service/base-svg-scraping.spec.js

core/base-service/base-xml.js

core/base-service/base-xml.spec.js

core/base-service/base-yaml.js

core/base-service/base-yaml.spec.js

core/base-service/base.js

core/base-service/base.spec.js

core/base-service/cache-headers.js

core/base-service/cache-headers.spec.js

core/base-service/deprecated-service.js

core/base-service/deprecated-service.spec.js

core/base-service/errors.js

core/base-service/index.js

core/base-service/legacy-request-handler.js

core/base-service/service-definitions.js