Return babe configuration information in the babe api epoch functions (#8072)

* Make changes

* Add serialize/deserialize, copy babe epoch config defaults from node runtime

* Fix line widths and turn default features off for serde

* Remove ser/deser from Epoch, fix node-cli

* Apply suggestions

* Add comment to BABE_GENESIS_EPOCH_CONFIG in bin

* Apply suggestions

* Add a sketchy migration function

* Add a migration test

* Check for PendingEpochConfigChange as well

* Make epoch_config in node-cli

* Move updating EpochConfig out of the if

* Fix executor tests

* Calculate weight for add_epoch_configurations

* Fix babe test

* Apply suggestions from code review

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

* Add more asserts to tests, remove unused changes to primitives/slots

* Allow setting the migration pallet prefix

* Rename to BabePalletPrefix

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>