(stable) Fix "AphrontRequest->getRequestURI()" for requests with "x[]=1" parameters in the URI

Summary:
Ref T13250. See PHI1069. This is a small fix for getRequestURI() currently not working if the request includes "x[]=..." PHP-flavored array parameters, beacause they're parsed into arrays by $_GET and setQueryParams(...) no longer accepts nonscalars.

Instead, just parse the raw request URI.

Test Plan: Visited /search/hovercard/?phids[]=X, no more fatal. Dumped the resulting URI, saw it had the right value. Tried ?phids[]=x&x=1&x=1&x=1, saw the parameters correctly preserved.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13250

Differential Revision: https://secure.phabricator.com/D20147