* viz: move sub-cmds using viz extension under viz cmd
Fixes#5327 , #5524
This branch moves the following commands, under the `linkerd viz`
cmd as they use the viz extension to perform the job.
- dashboard
- edges
- routes
- stat
- tap
- top
This also creates a new pkg `public-api` which fecilitates
interaction and communication with public-api to be used
across extensions.
Signed-off-by: Tarun Pothulapati <tarunpothulapati@outlook.com>
Co-authored-by: Alex Leong <alex@buoyant.io>
Tarun Pothulapati
Mayank Shah