Do not close the inner reader when disposing wrapped data readers

[0xced]

When disposing wrapped readers, only call Dispose() on the inner reader and let it catch exceptions if appropriate.

Note: this actually happened with Microsoft.Data.SqlClient.

Microsoft.Data.SqlClient.SqlException (0x80131904): Execution Timeout Expired.  The timeout period elapsed prior to completion of the operation or the server is not responding.
 ---> System.ComponentModel.Win32Exception (258): The wait operation timed out.
   at void Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, bool breakConnection, Action<Action> wrapCloseInAction)
   at void Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, bool callerHasConnectionLock, bool asyncClose)
   at bool Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, out bool dataReady)
   at bool Microsoft.Data.SqlClient.SqlDataReader.TryCloseInternal(bool closeReader)
   at void Microsoft.Data.SqlClient.SqlDataReader.Close()
   at void Dapper.DbWrappedReader.Dispose(bool disposing) in /_/Dapper/WrappedReader.cs:line 149
   at ValueTask System.Data.Common.DbDataReader.DisposeAsync()

[mgravell]

Seems fair; we can let the inner reader worry about what Dispose() means, since we're propagating Dispose(), not Close() + Dispose().

[mgravell]

overriding appveyor, although the pgsql problem might prevent "main" deploy - that's not your problem, though; unrelated to this PR