mw.loader: Use Array#indexOf directly instead of jQuery.inArray

mw.loader: Use Array#indexOf directly instead of jQuery.inArray

Unlike other jQuery methods (which are quite often significantly
faster or slower than native methods), jQuery.inArray is quite
literally a wrapper around Array#indexOf. Use it directly where
possible.

Also:
* Replace `$.inArray(val, [a, b]) !== -1` pattern
  with `val === a || val === b` which is upto 10x faster.
* mw.loader.store.set.: Remove redundant parenthesis in nested expression.

Change-Id: Ia2b922b3245bfb39b609b57e84938317e9c89cd6