Update to latest QGIS release (3.40.2) and up vcpkg revision to prepare for Qt 6.8.2

[nirvn]

Title says it all

[qfield-fairy]

🎉 Ta-daaa, freshly created APKs are available for 9e26119: arm64-android

Other architectures

• arm-neon-android
• x64-android
• x86-android
• all access arm64-android
• all access arm-neon-android
• all access x64-android
• all access x86-android

[m-kuhn]

Fantastic work @nirvn .
Do we finally need to keep the vcpkg-make overlay?

Regarding the other two overlays, can we leave a sentence somewhere to remind us why we have these (and that will help us remember what's needed to go back to the base registry for them)?

[nirvn]

@m-kuhn , you are correct, we don't need the port now that we downgraded libb2. For the record, to my own future self or others, that port was needed to fix the macos compilation, not iOS. We were hitting this issue being address in this PR (microsoft/vcpkg#43121) on macos.

As for the two added ports, I've filed an issue for libb2 here to raise the ongoing build failure on iOS: microsoft/vcpkg#43326

For zxing-cpp, the issue has to do with its version 2.3 having upgraded the minimum c++ version to 20. I think we can downgrade here for a while and try again in a year or so :) not sure it's worth opening an issue with vcpkg itself on this one.