Make XDGShellV5 co-compilable with XDGWMBase

Summary:
When we add WMBase (the new name stable XdgShell)  we get a clash with
XDGShellV5. This clash consists of all functions in the generated C file
which clashes at linker time, as well as multiple xdg_blah_interface
structs which would get redefined.

XDGShellV5 in practice is used by literally no-one (Qt never defaulted
to it if wl-shell was available) and has been dropped from GTK when
they added v6. But it's used by some kwin unit tests so breaking
would cause issues for stable kwin release tests... so it's a pain.

We can't mod the XML as we need the strings sent down the wire to remain
the same and we need the same names for our forward declared structs
that the client code can cast to.

This patch copies the generated files and modifies them manually.
Hacky, but we know this code will never change again - and IMHO this
task isn't one worth investing too much time into.

Test Plan:
Finished my XDG WM Base patch (see next phab) and things compile \o/

Unit test still passes

Ran: QT_WAYLAND_SHELL_INTEGRATION=xdg-shell-v5 dolphin --platform wayland and verified it worked

Reviewers: #plasma, romangg

Reviewed By: #plasma, romangg

Subscribers: romangg, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D13488