Add nav bar item to show HCP link status and encourage folks to link

[dhiaayachi]

Description

We want people to link to HCP!
This PR adds a nice little nav bar item to the sidebar letting users view their linked clusters in HCP as well as begin the linking process. (Although the actual linking start - with modal will happen in https://hashicorp.atlassian.net/browse/CC-7147

Testing & Reproduction steps

• Just open this up
  • yarn start
  • localhost:4200/ui
• You should see the purple banner and a new nav icon in the sidebar
• If you dismiss the banner, the New Item should go away
• If you've already linked your cluster (Update this to STATE_TRUE) and restart ui server - you should see a link to HCP consul
• If you pretend to be an hcp hosted consul, you should see the ol Back to HCP link
  • To enable: Scenario('CONSUL_HCP_ENABLE=1'); and Scenario('CONSUL_HCP_URL=https://corn.com')
  • To disable: delete them from your cookies

Links

• Jira

Screenshots

References