Add troubleshooting guidance for SQL Encrypt breaking change

[mikeminutillo]

Microsoft.Data.SqlClient version 4 includes a breaking change dotnet/SqlClient#1210 which causes existing clients to throw an exception when using the default configuration:

System.Data.SqlClient.SqlException
  HResult=0x80131904
  Message=A connection was successfully established with the server, but then an error occurred during the login process. (provider: SSL Provider, error: 0 - The certificate chain was issued by an authority that is not trusted.)
  Source=.Net SqlClient Data Provider

[tmasternak]

LGTM

Minor question: can we remove duplication from the guidance files?

[mikeminutillo]

Duplication (mostly) removed. I pulled the guidance out of the individual upgrade guides and created a specific upgrade guide for upgrading to SqlClient 4 in both SQL-T and SQL-P. The ServiceControl one has slightly different text so I left it as a "duplicate"

[timbussmann]

minor nitpick