Add changes for edge-20.2.3

[kleimkuhler]

edge-20.2.3

This release introduces the first optional add-on tracing, added through the
new add-on model!

The existing optional tracing components Jaeger and OpenCensus can now be
installed as add-on components.

There will be more information to come about the new add-on model, but please
refer to the details of #3955 for how to get started.

• CLI
  • Added the linkerd diagnostics command to get metrics only from the
    control plane, excluding metrics from the data plane proxies (thanks
    @srv-twry!)
  • Added the linkerd install --prometheus-image option for installing a
    custom Prometheus image (thanks @christyjacob4!)
  • Fixed an issue with linkerd upgrade where changes to the Namespace
    object were ignored (thanks @supra08!)
• Controller
  • Added the tracing add-on which installs Jaeger and OpenCensus as add-on
    components (thanks @Pothulapati!!)
• Proxy
  • Increased the inbound router's default capacity from 100 to 10k to
    accommodate environments that have a high cardinality of virtual hosts
    served by a single pod
• Web UI
  • Fixed styling in the CallToAction banner (thanks @aliariff!)

[admc]

👍