Reorganize cAdvisor package / directory hierarchy

[timstclair]

Problem: The cAdvisor directory / package organization is flat and lacks intuitive structure. This makes it hard for new developers to find and understand the relevant parts of the code, and it makes it difficult for users to separate code from utility and API.

Proposed changes:

• Rename ‘info’ to ‘api’ - more intuitive, matches k8s structure
• Group together server code under a single “server” parent package
  • Includes: api (current definition, not info), pages (UI), http, healthz, validate
  • Rename ‘pages’ to ‘ui’
• Non-code - due to flat structure, tests, build and deploy all live on the same level. Would be nice to have a little more structure to separate
• Clients - Tracked in Clean up go clients #1180
• Organize cAdvisor root
  • Move *.go to ‘cmd’ or ‘main’ package
  • Add a ‘test’ directory, move ‘integration’ to ‘test/integration’, move ‘test.http*’ to ‘test/’
• Rename ‘metrics’ to ‘prometheus’
• Consider: move internal packages (manager, container, fs, collector, etc.) under a common root (e.g. ‘internal’, ‘lib’, or ‘pkg’) - this will make finding the integration points easier for new users

[Thiht]

I'd be glad to help with the clients refactoring and improvements since I'm using them right now.

[timstclair]

@Thiht - Awesome! I filed a separate tracking issue for you to use: #1180