Introduce the migration guide to track 2 modules (#14980)
Introduce the migration guide to track 2 modules (#14980)

* migration guide

* resolve comments

* move the migration guide to documentation directory

* fix typo

* resolve comments

* resolve comments
Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go