Repackage encodeURI and encodeURIComponent as builtin functions
and install them in the bootstrapper.

Crude benchmark on 351 encodeURI and encodeURIComponent tests averaged
over five runs:

* builtin functions
real	0m8.01s
user	0m18.00s
sys	0m7.37s

* JS functions calling into the runtime e.g., for %NewString
real	0m8.44s
user	0m19.52s
sys	0m7.49s

By running:
$ time tools/run-tests.py   --arch=x64 --mode=Release --buildbot
mjsunit/uri test262/built-ins/encodeURI*
>>> Running tests for x64.Release

BUG=v8:4912
R=yangguo@chromium.org

Review-Url: https://codereview.chromium.org/1983593002
Cr-Commit-Position: refs/heads/master@{#36273}