fix(ngSwitch): use the correct transclusion scope

If an ngSwitchWhen or ngSwitchDefault directive is on an element that also
contains a transclusion directive (such as ngRepeat) the new scope should
be the one provided by the bound transclusion function.

Previously we were incorrectly creating a simple child of the main ngSwitch
scope.

BREAKING CHANGE:
** Directive Priority Changed ** - this commit changes the priority
of `ngSwitchWhen` and `ngSwitchDefault` from 800 to 1200.  This makes their
priority higher than `ngRepeat`, which allows items to be repeated on
the switch case element reliably.

In general your directives should have a lower priority than these directives
if you want them to exist inside the case elements. If you relied on the
priority of these directives then you should check that your code still
operates correctly.

Closes #8235
fix(ngSwitch): interoperate with multi-element transclude directives

Worked with @lgalfaso on the implementation here.

Closes #8235
Closes #8244