infopanel: Add choice of date display formats

Summary:
Let user choose date display format via checkbox in context menu

[[ https://phabricator.kde.org/file/info/PHID-FILE-5xjr7tvypj3jaczjtzrz | Example ]]

Depends on D11242

FEATURE: 392352

Test Plan: visual inspection

Reviewers: #dolphin, markg, ngraham

Reviewed By: markg, ngraham

Subscribers: broulik, markg, ngraham

Tags: #dolphin, #kde_applications

Differential Revision: https://phabricator.kde.org/D11245