istio: add non-mcp test variants to testgrid dashboard
istio: add non-mcp test variants to testgrid dashboard

Istio is switching to MCP by default. During the transition we'd like
to retain testing a subset of the non-mcp. We'd also like to retain
the previous mcp specific test results in testgrid for a few weeks
until the cutover completed.

GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid