refactor: manager extract readLocalFile instead of platform.getFile

lib/manager/bundler/extract.spec.ts

lib/manager/bundler/extract.ts

lib/manager/composer/extract.spec.ts

lib/manager/composer/extract.ts

lib/manager/gradle/index.spec.ts

lib/manager/gradle/index.ts

lib/manager/helm-requirements/extract.spec.ts

lib/manager/helm-requirements/extract.ts

lib/manager/npm/extract/index.spec.ts

lib/manager/npm/extract/index.ts

lib/manager/npm/extract/npm.spec.ts

lib/manager/npm/extract/npm.ts

lib/manager/npm/extract/yarn.spec.ts

lib/manager/npm/extract/yarn.ts

lib/workers/repository/extract/manager-files.spec.ts

lib/workers/repository/extract/manager-files.ts