Remove old code in v8::Date::DateTimeConfigurationChangeNotification
Add code to clear date time cache object in isolate.

Running benchmark
python -u tools/run_perf.py --binary-override-path \
  out/x64.release/d8 --filter "JSTests/Strings/StringLocaleCompare" \
  test/js-perf-test/JSTests.json
python -u tools/run_perf.py --binary-override-path \
  out/x64.release/d8 --filter "JSTests/Dates" \
  test/js-perf-test/JSTests.json
python -u tools/run_perf.py --binary-override-path \
  out/x64.release/d8 --filter "JSTests/Numbers" \
  test/js-perf-test/JSTests.json

BEFORE THE FIX:
StringLocaleCompare-Strings(Score): 184287
toLocaleDateString-Dates(Score): 10456
toLocaleString-Dates(Score): 10436
toLocaleTimeString-Dates(Score): 10700
toLocaleString-Numbers(Score): 2935

AFTER THE FIX in Patch Set 13:
StringLocaleCompare-Strings(Score): 57470000
toLocaleDateString-Dates(Score): 6141000
toLocaleString-Dates(Score): 4093000
toLocaleTimeString-Dates(Score): 6323000
toLocaleString-Numbers(Score): 3371000

Bug: chromium:901748, chromium:901747, v8:5751
Change-Id: I7578e2ced0fe967dce6424d17f15ab806cc522be
Reviewed-on: https://chromium-review.googlesource.com/c/1320892
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57484}