Frame.ofRecords creates duplicated columns for F# records

[gbtb]

Basically, due to how F# compiler lowers record fields to IL, for each field we will have both Property and Field with @ suffix generated.
For example, https://sharplab.io/#v2:DYLgZgzgNAJiDUAfALgTwA4FMAEAVA9ugJYDGAIphCQE5HrJH4B22AvNgN4CwAUNv9gDKmagDcRIbBGS0mAc14C8hUpOmyFPAL5A.

The code in

Deedle/src/Deedle/FrameUtils.fs

Line 88 in 93c624e

let getMemberProjections (recdTy:System.Type) =

doesn't account for that, and it causes creation of duplicated columns for a record.

getExpandableFields tries to filter out non-public properties, but for some reason it doesn't work with compiler-generated internal fields@, so ,I guess, it should probably additionally filter out fields with [CompilerGenerated] attribute on them.