Duplicate segment override priorities when adding new overrides in versioned environments

[matthewelwell]

Given:

Environment A (Feature versioning enabled)
Segment A
Segment B
Feature A

To reproduce:

1. Create a segment override for Segment A on Feature A and update segment overrides
2. Create another segment override for Segment B on Feature A and update segment overrides

Notice the following issues:

1. When creating the version for the creation of the second segment override, the FE sends the (unchanged) override in "feature_states_to_update" in the POST request.
2. In the subsequent call to retrieve the feature states for the Feature A, both overrides have the same priority.

[matthewelwell]

Resolved by #4609 and #4603