filenameseearch: Full decode search and url parameter

To allow passing parameters that contain cararcters that need caracter encoding.

With a query such as:

~/kde6/build/kde-cli-tools/bin/kioclient ls "filenamesearch://?search=test%C3%A9.%2A&url=file%3A%2F%2F%2Fhome%2Fmeven%2FTéléchargements

Allows to find correct answer files starting with "testé".