This is a prep commit for typescript migration of this module. In this commit
I made all the users of ListWidget pass generic sort functions like 'alphabetic'
and 'numeric' explicitly to avoid type conversions which we may need when moving
to typescript, also it simplifies our `set_sorting_function` a bit more.
Implemented date localization using native Intl object.
Created special function get_localized_date_or_time_for_format
Made necessary string formatting changes in 'timerender.ts'.
Fixed tests and added some localization tests too.
Tested on my local development server, with some random languages.
Fixes#23987.
This lets us simplify the long-ish ‘../../static/js’ paths, and will
remove the need for the ‘zrequire’ wrapper.
Signed-off-by: Anders Kaseorg <anders@zulip.com>