fix(s2n-quic-transport): allow migrations even when disable_active_migration is sent

[WesleyRosenblum]

Release Summary:

Connection migrations are now allowed even when the disable_active_migration is set to true, as it is not possible to distinguish between the peer performing an active migration, and a NAT rebind.

Description of changes:

This change loosens two restrictions on connection migration:

1. Migrations are now allowed even if the disable_active_migration transport parameter is set to true
2. Migrations are allowed even if the peer did not supply sufficient connection IDs to allow for using a new connection ID on the new path

The reasoning for allowing migrations in these cases is that there is no way a server can definitely determine that a migration from the peer was intentional/active versus just a NAT rebind. The peer is allowed to change destination connection IDs at any time, so if a peer undergoes a NAT rebind at the same time they change destination CID, that would appear identical to an active migration. To increase availability, we will allow such cases to proceed with migration.

Testing:

Updated existing unit test

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