Support urldecoded URLs in current menu item detection logic

[soulseekah]

When adding a urldecoded custom link to a menu it is not being detected as the current one when visiting it.

This doesn't work:

​http://example.org/привет/
/привет/

This works:

​http://example.org/%D0%BF%D1%80%D0%B8%D0%B2%D0%B5%D1%82/
/%D0%BF%D1%80%D0%B8%D0%B2%D0%B5%D1%82/

[soulseekah]

Initial tests

[soulseekah]

Initial patch

[soulseekah]

Props to @campusboy1987 for discovering and describing the issue.

[campusboy1987]

I checked the edits of @soulseekah on a couple of sites where such a problem arose. Now everything works fine! I'm looking forward to the resilience. Gennady (@soulseekah), thanks for the quick response and solution.

[SergeyBiryukov]

In 42732:

Menus: When checking if a Custom Link matches the current URL to add the current-menu-item class, check for decoded URL as well.

Props soulseekah, campusboy1987.
Fixes #43401.