feat(datasource/helm): optimize sourceurl massaging (#11794)

lib/datasource/helm/__fixtures__/index.yaml

lib/datasource/helm/__fixtures__/sample.yaml

lib/datasource/helm/__snapshots__/index.spec.ts.snap

lib/datasource/helm/common.spec.ts

lib/datasource/helm/common.ts

lib/datasource/helm/index.ts

lib/datasource/helm/types.ts