So this means, if you use default StandardCodec, and 3 fields store
doc values, and "main" CFS is off but doc values CFS is on, you'll see
a cfs file holding the 3-6 sub-files that your docvalues created,
But eg if some fields use another codec, then that codec will have its
own CFS for any fields it has with docvalues (this is the TODO)?
That's seems fine for starters.
I like CodecConfig, but I'm not sure it should hold things specific
only to 1 codec, like the Pulsing cutoff? The other settings seem
more widely applicable... though I guess even terms cache size is not
used by various codecs, but it is by enough to have it in
CodecConfig, I think?
CodecConfig needs @experimental?
For the nested test... couldn't you createCompoundOutput directly from
an opened CompoundFileDirectory? (Vs creating externally & copying