Due diligence on new DbDataReader extension method class on System.Data.Common

[divega]

This issue to make sure we follow up with @terrajobst to make sure we do the right thing for the new extension method sponsor class to be created in dotnet/corefx#36123.

Possible concerns are:

1. Should the class be included in .NET Standard 2.1?
2. Understand in which of the TFMs targeted by the System.Data.Common package the methods will be available

cc @roji @ajcvickers

[roji]

@divega, #27059 has the api-candidate-for-standard label and this issue doesn't seem to contain anything more beyond that - can we close?

[divega]

Closing as we have scheduled this for API review.