Add workspace CLI command, list/inspect subcommands

[catsby]

This PR introduces a top level command tree workspace that is scoped to the current context, with two subcommands:

• list: list all workspaces in this context
• inspect <name>: inspect the workspace <name>, or the current workspace

This PR builds off of #2353 so I'm opening it as a draft until 2353 is approved and merged. Until then this PR will appear to be larger than it actually is. #2353 has been merged

UX:

List:

$ waypoint workspace list                  
   NAME   |        PROJECTS
----------+--------------------------
  default | example-go,example-ruby
  dev     | example-go
  lab     | example-ruby,example-go

Inspect the default workspace:

$ waypoint workspace inspect               

» Workspace Info:
             Name: default
  Latest activity: 22 minutes ago
         Projects: example-go,example-ruby

Inspect workspace by name:

$ waypoint workspace inspect dev

» Workspace Info:
             Name: dev
  Latest activity: 28 minutes ago
         Projects: example-go

[evanphx]

Looks good!

[briancain]

Nice! Love to get more inspection tools on the CLI. Looks good. Most of my comments are pretty minor fixups 😄 👍🏻