Refine component lifecycle hooks

[wycats]

This commit refines the lifecycle hooks to more completely support the
use-cases.

On first render (in order):

• didInitAttrs runs after attrs is guaranteed to be up to date. This
  is more reliable than trying to ensure that attrs are always
  available on init.
• didReceiveAttrs runs after didInitAttrs (it also runs on
  subsequent re-renders, which is useful for logic that is the same
  on all renders).
• willRender runs before the template is rendered. It runs when the
  template is updated for any reason (both initial and re-render, and
  regardless of whether the change was caused by an attrs change or
  re-render).
• didInsertElement runs after the template has rendered and the
  element is in the DOM.
• didRender runs after didInsertElement (it also runs on subsequent
  re-renders).

On re-render (in order):

• didUpdateAttrs runs when the attributes of a component have changed
  (but not when the component is re-rendered, via component.rerender,
  component.set, or changes in models or services used by the
  template).
• didReceiveAttrs, same as above.
• willUpdate runs when the component is re-rendering for any reason,
  including component.rerender(), component.set() or changes in
  models or services used by the template.
• willRender, same as above
• didUpdate runs after the template has re-rendered and the DOM is
  now up to date.
• didRender, same as above.

Note that a component is re-rendered whenever:

1. any of its attributes change
2. component.set() is called
3. component.rerender() is called
4. a property on a model or service used by the template has changed
   (including through computed properties).

Because of the Glimmer engine, these re-renders are fast, and avoid
unnecessary work.