Preprocessing routines fail if there is a dot in the config "keys"

I found that preprocessing routines fail when there is a dot in one of the "keys" of the preprocessing config.

Example: I was trying to run preproc_or_load_group. One of my entries in the config looked like

name: "atomic_info"
process:
    noise_ratio_Q.rmean: rmeanQ

This caused an error on line 1118 https://github.com/simonsobs/sotodlib/blob/ff8363852eb76af4f610a117b6341b806c80d3a2/sotodlib/preprocess/preprocess_util.py#L1118

It seems the problem is actually in get_pcfg_check_aman which is trying to save noise_ratio_Q.rmean as an AxisManager with the single entry rmeanQ. It successfully does this but later when you try to save the aman, it thinks noise_ratio_Q.rmean is looking for a child of another aman noise_ratio_Q and throws an error.

I've done a workaround (swapping the key/value in my pair the order didn't matter) but thought best to flag.