[Development] PSA: Merging changes to qtqa and info about submodule integration license checking

[Alexandru Croitor]

Hi,

For a while now we had a slightly weird branching situation in qtqa, 
where we had a master and a dev branch, and it was a bit unclear what is used where.

Here's a summary of latest changes regarding that situation.

1) Since a few months, qt submodule integrations (qtbase, qtsvg, etc) 
in the dev branch, are using license checking code from qtqa/dev.
https://codereview.qt-project.org/c/qt/qt5/+/578757

Going forward, when 6.9 branches, it will use qtqa/6.9. Same for 6.10, etc.


2) Since around a week, qt submodule integrations in the 6.8 branch, 
are using license checking code from qtqa/6.8.
https://codereview.qt-project.org/c/qt/qt5/+/585799


3) For integrations in the private 5.15 and 6.5 branches, 
license checking code will continue to use qtqa/master.
This was recently broken when (1) landed, but should be fixed now 
thanks to https://codereview.qt-project.org/c/qt/qtqa/+/599793


4) In the near future we will likely branch qtqa/6.5, and cherry-pick (1), so that
6.5 integrations also follow the usual branching scheme like (1) and (2).
When / if that happens, we'll send a mail.


5) qtqa/master will likely be kept alive until the private 5.15 branch is closed.


6) When making qtqa license checker changes, consider pushing to dev and adding 
Pick-to: 6.8 master

Once (4) is done add
Pick-to: 6.8 6.5 master

Once 6.9 is branched add
Pick-to: 6.9 6.8 6.5 master