Bug 1635764 - Move --with-system-icu and --with-intl-api to python configure....

Bug 1635764 - Move --with-system-icu and --with-intl-api to python configure. r=firefox-build-system-reviewers,rstewart

At the same time, because it's now simpler to do so, set the right data
file name for big-endians, even though we don't have or produce it
(bug #1264836). Also remove USE_ICU, which is redundant with
JS_HAS_INTL_API, and actively break the build at configure time when
using --without-intl-api with Firefox because this hasn't actually
worked for close to 3 years (since bug 1402048).

Differential Revision: https://phabricator.services.mozilla.com/D77416