IngestExternalFileOptions::fill_cache may not work when there is concurrent MANIFEST writer

[cbi42]

The table files opened during MANIFEST write uses the read option from the MANIFEST writer:

rocksdb/db/version_set.cc

Line 5608 in 20d065d

read_options);

. Since we do group MANIFEST writes, it's possible that the read options used to open table files may not match the intended read option, e.g. from

rocksdb/db/db_impl/db_impl.cc

Line 6068 in 20d065d

versions_->LogAndApply(cfds_to_commit, read_options, write_options,

. For example, this can cause fill_cache to not working as expected.