not sure how these would even work with mvcc - either way, an ephemeral
table use an ephemeral database file and pager so i don't think putting
its writes into MV store makes sense
TBH i have no idea if there are any weird interactions here but the code
we have now for sure does not work
Closes#3486
Reviewed-by: Nikita Sivukhin (@sivukhin)
Closes#3490