MDEV-31608 - Connector/NET fails to connect since 10.10

Connector/NET does not expect collation IDs returned by "show collations"
to be NULL, runs into an exception.

The fix is to determine connector/net using its connection attributes,
then make sure "show collations" does not output NULL IDs.

The patch introduces new old_mode NO_NULL_COLLATION_IDs, that is
automatically set, once MySQL Connector/NET connection is determined.

A test was added, that uses MySql.Data from powershell - only works
if MySql.Data is installed into GAC (i.e with C/NET MSI package)

mysql-test/main/mysql_connector_net.ps1

@@ -0,0 +1,58 @@
+$assembly = [system.reflection.Assembly]::LoadWithPartialName("MySql.Data")
+if ($assembly -eq $null)
+{
+  "Can't load assembly MySql.Data"
+  exit 100
+}
+
+try
+{
+  $connectionString =[string]::Format("server=127.0.0.1;uid=root;port={0};Connection Reset=true;",$Env:MASTER_MYPORT)
+  $connection = [MySql.Data.MySqlClient.MySqlConnection]@{ConnectionString=$connectionString}
+  $connection.Open()
+
+  # Test ExecuteReader()
+  $command = New-Object MySql.Data.MySqlClient.MySqlCommand
+  $command.Connection = $connection
+  $command.CommandText = "SELECT @@old_mode"
+  $reader = $command.ExecuteReader()
+  $reader.GetName(0)
+  while ($reader.Read())
+  {
+    $reader.GetValue(0)
+  }
+
+  # Test connection reset
+  $connection.Close()
+  $connection.Open()
+  # Test ExecuteNonQuery()
+  $command.CommandText="do 1";
+  $affected_rows = $command.ExecuteNonQuery()
+  if ($affected_rows -ne 0)
+  {
+    "Expected affected rows 0, actual $affected_rows"
+    exit 1
+  }
+  # Test Prepared Statement
+  $command.CommandText = "SELECT @var";
+  [void]$command.Parameters.AddWithValue("@var", 1);
+  $command.Prepare();
+  $out = $command.ExecuteScalar();
+  if ($out -ne 1)
+  {
+    "Expected output 1, actual $out"
+    exit 1
+  }
+  $connection.Close()
+}
+catch
+{
+  # Dump exception
+  $_
+  $inner = $PSItem.Exception.InnerException
+  if ($inner -ne  $null)
+  {
+    $PSItem.Exception.InnerException.Message
+    $PSItem.Exception.InnerException.StackTrace
+  }
+}