https://www.figma.com/file/4sXj42XyicBsdQkYIugHaV/Compass-Import%2FExport?node-id=1136%3A47745&t=waeIls8QO2JWTpSd-1 

In the import modal `Specify Fields and Types` table, add a skeleton loading status while we analyze the CSV fields and types. Let's reuse the skeleton we show for the collections tree.

In this work we start running `analyzeCSVFields`. Add a `mixed` data type field. This is also re-run when the delimiter is re-selected. We'll already have the first few csv fields, however we can't pre-select the types until we've analyzed the csv fields.