fix(*): detect external changes in `history.state`

Previously, `$browser.$$checkUrlChange()` (which was run before each `$digest`)
would only detect an external change (i.e. not via `$location`) to the browser
URL. External changes to `history.state` would not be detected and propagated to
`$location`.

This would not be a problem if changes were followed by a `popstate` or
`hashchange` event (which would call `cacheStateAndFireUrlChange()`). But since
`history.pushState()/replaceState()` do not fire any events, calling these
methods manually would result in `$location` getting out-of-sync with the actual
history state.

This was not detected in tests, because the mocked `window.history` would
incorrectly trigger `popstate` when calling `pushState()/replaceState()`, which
"covered" the bug.

This commit fixes it by always calling `cacheState()`, before looking for and
propagating a URL/state change.