URLHandler: remove percent encoding if the entire URL is encoded
However, we may not always decode the URL especially if only components are encoded. This adds a logic to determine the encoding state of the provided URL parameter.
In 2015 with VLC-iOS 2.4 we did not specify the encoding state of the URL parameter so many competing implementations exist.
Fixes #1297 (closed) and its duplicates
(cherry picked from commit 8341da11, backport of !655 (merged))