[Backport release-3_10] Windows GPKG project storage: fix path encoding

[qgis-bot]

Backport 42ea7bc from #36980

[agiudiceandrea]

@elpaso, it seems to me that the issue #36832 (at least the first reported behaviour) was not reproducible on 3.10.6 because #33265, which introduced the issue, was not backported to 3.10 afaik.
Is it safe to backport this fix to 3.10? without backporting also #33265?

[elpaso]

@agiudiceandrea the real fix turned out to be https://github.com/qgis/QGIS/pull/36993/files#diff-f333e375c59b5479cf267e8d70180df7R383

The root of the problem was the way the connection path is stored when a new connection is automatically created after the user creates a new GPKG (i.e. \ was used instead instead of /, which is supported on windows too).

I checked 3.10 and the code is the same so I think it's safe to backport. Are you sure the issue does not exist in 3.10?

It can be checked by creating a new GPKG, opening the settings file of the active profile and checking for the path stored in for the newly created GPKG stored connection: if it uses \ then we have the problem.

A manual test of this backport after merge would be appreciated as well.

[nyalldawson]

Lets queue this for 3.10.9 to give plently of time for testing in 3.14 then...

[nyalldawson]

Moved to #36812