Improve performance documentation and environment

[siggy]

This change provides a more user-friendly environment for testing Linkerd performance. Changes include:

• Introduce Grafana Docker build for performance testing
• Better node affinity / taint instructions
• Microsecond latency resolution
• More canonical Prometheus config, similar to Linkerd2's control plane

Signed-off-by: Andrew Seigner siggy@buoyant.io