This reducer doesn't really add value, because:

 (a) it is only concerned with JSCallFunction and JSToNumber, but when
     we get to it, all JSCallFunction nodes will have been replaced by
     Call nodes, and in the not so far future, we will also have
     replaced almost all JSToNumber nodes with better code,
 (b) and the reducer tries to be smart and use one of the outermost
     contexts, but that might not be beneficial always; actually it
     might even create longer live ranges and lead to more spilling
     in some cases.

But most importantly, the JSContextRelaxation currently blocks inlining
based on SharedFunctionInfo, because it requires the inliner to check
the native context, which in turn requires JSFunction knowledge. So I'm
removing this reducer for now to unblock the more important inliner
changes.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1715633002

Cr-Commit-Position: refs/heads/master@{#34139}