Use ICU to check ID_Start, ID_Continue and WhiteSpace even for BMP
when V8_INTL_SUPPORT is on (which is default).

Change LineTerminator::Is() to check 4 code points from
ES#sec-line-terminators instead of using tables and Lookup function.

Remove Lowercase::Is(). It's not used anywhere.

Update webkit/{ToNumber,parseFloat}.js to have the correct expectation
for U+180E and the corresponding expected files. This is a follow-up to
an earlier change ( https://codereview.chromium.org/2720953003 ).

CQ_INCLUDE_TRYBOTS=master.tryserver.v8:v8_win_dbg,v8_mac_dbg;master.tryserver.chromium.android:android_arm64_dbg_recipe
CQ_INCLUDE_TRYBOTS=master.tryserver.v8:v8_linux_noi18n_rel_ng

BUG=v8:5370,v8:5155
TEST=unittests --gtest_filter=CharP*
TEST=webkit: ToNumber, parseFloat
TEST=test262: built-ins/Number/S9.3*, built-ins/parse{Int,Float}/S15*
TEST=test262: language/white-space/mong*
TEST=test262: built-ins/String/prototype/trim/u180e
TEST=mjsunit: whitespaces

Review-Url: https://codereview.chromium.org/2331303002
Cr-Commit-Position: refs/heads/master@{#45957}