This commits ports the `search_operators.html` file from
./templates to handlebars, essentially creating a new file
as `search_operators.hbs` within /static/templates which is
then rendered using info_overlays.js.
As part of this migration, we rewrote the way internationalization was
done, since the previous implementation incorrectly did not support
languages with a different word order than English.
We also not consistently use periods at the end of the descriptions.
Co-authored-by: Tim Abbott <tabbott@zulip.com>
Fixes#18504.
aryanshridhar