Move functions into anonymous namespce.
Remove dead code.
Move GetCaseFirst into JSCollator
Move HourCycle, ToHourCycle and GetHourCycle into JSDateTimeFormat

Change-Id: Ie6089e7f33677dd40169c56198b52d87ba490b20
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2067689
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66395}