integrate zones list endpoint MAASENG-1975

[petermakowski]

Done

• integrate zones list endpoint MAASENG-1975
  • call /MAAS/a/v1/zones REST endpoint instead of zone.list websocket API whenever zone/fetch redux action is called
  • reduce redundant tests nesting in describe("http sagas", () => {

QA

QA steps

• open developer tools and go to Network tab
• Go to machines list
• Verify that zones list has been fetched via REST API (should be in Fetch/XHR list) and there is no zone.list in websocket messages

Fixes

Fixes: https://warthogs.atlassian.net/browse/MAASENG-1975

[webteam-app]

Demo starting at https://maas-ui-5071.demos.haus