Improve localization of search box and date filters

Description

Original report: https://community-release.mattermost.com/core/pl/7rk7eb3i9pyajxj5sym88ugz3r

To better localize the search box and date picker, we should do the following:
1. Allow the `on`, `before`, `after`, etc search filters to be localized. This should be reflected in the help tooltip on the search box.
2. Add the correct date format to the help text tooltip on the search box


3. Localize the month and days in the date picker using the built-in localization that's part of react-date-picker.

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Reporter

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Mana

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Unassigned

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Reporter

Amy Blais

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Fix versions

Mattermost Team

Platform

Sprint

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