[azeventhubs] Adding in a section about TCP connection sharing to the migration guide (#19200)
[azeventhubs] Adding in a section about TCP connection sharing to the migration guide (#19200)

Adding in a section about TCP connection sharing, which is an important (but understated) feature.
Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go