[kio_http] Parse a FullyEncoded QUrl path with TolerantMode

When using url.setPath(otherUrl.path(FullyEncoded)), we have to specify the
TolerantMode parsing mode (setPath uses DecodedMode by default), otherwise
we end up with a doubly encoded url:

otherUrl.path(FullyEncoded) would represent a space as %20 then
url.setPath(otherUrl.path(FullyEncoded), DecodedMode) would represent
the '%' character with '%25' so the path ends up with '%2520'.

AFAIU, either we use:
url.setPath(otherUrl.path(FullyDecoded), DecodedMode) OR
url.setPath(otherUrl.path(FullyEncoded), TolerantMode)

url.path() and url.setPath use FullyDecoded and DecodedMode by default,
respectively.

Thanks to Andreas Schwab for figuring it out in the bug report.

BUG: 386406
FIXED-IN: 5.71.0