Re-implement the WantMassQuery property of binary caches

src/libstore/binary-cache-store.cc

src/libstore/binary-cache-store.hh

src/libstore/http-binary-cache-store.cc

src/libstore/local-store.cc

src/libstore/nar-info-disk-cache.cc

src/libstore/nar-info-disk-cache.hh

src/libstore/s3-binary-cache-store.cc

src/libstore/store-api.hh