b239e92eb6
This change adds setup for a second tailnet to enable multi-tailnet e2e tests. When running against devcontrol, a second tailnet is created via the API. Otherwise, credentials are read from SECOND_TS_API_CLIENT_SECRET. Also adds an l7 HA Ingress test for multi-tailnet. Fixes tailscale/corp#37498 Signed-off-by: Becky Pauley <becky@tailscale.com>