Pooled normals for CNVkit

[HenriettaHolze]

Description of feature

Hi, CNVkit recommends to pool all normal samples, instead of using one matched normal sample for each tumor sample https://cnvkit.readthedocs.io/en/stable/pipeline.html#paired-or-pooled-normals.
Could you please implement an option, similar to --joint_germline and --joint_mutect2, to use multiple or all normal samples as CNVkit reference?

Thanks a lot!