* [ML][Data Frame] Adding bwc tests for pivot transform (#43506)
* [ML][Data Frame] Adding bwc tests for pivot transform
* adding continuous transforms
* adding continuous dataframes to bwc
* adding continuous data frame tests
* Adding rolling upgrade tests for continuous df
* Fixing test
* Adjusting indices used in BWC, and handling NPE for seq_no_stats
* updating and muting specific bwc test
* Adjusting bwc tests for backport