TestSuite: added "docking_dockspace_copy_no_remap"

[PathogenDavid]

Regression test for ocornut/imgui#6035

Verified by intentionally regressing ocornut/imgui@6939676

[PathogenDavid]

This test was originally failing only for Linux docking on CI.

I did not have time to fully investigate why it was failing, but based on a hunch from a similar issue with #19 I guessed it was due to Window0 being too small, and indeed adding a SetNextWindowSize call for it fixed the issue.

I can investigate further if you find that fix unsatisfactory. It'd definitely be nice to know why Linux docking CI in particular seems to find these issues, but it might be a deep rabbit hole too. (I tested locally with WSLg and it passed there, which suggests it might be CI-specific rather than Linux docking-specific.)

I know for #19 I ended up figuring out that ImGuiTestContext::GetWindowTitlebarPoint was picking an invalid point on super small windows (had a note to report / investigate a fix later -- IIRC it looked like it was due to not avoiding the close/window menu buttons.), might just be the same issue manifesting its self slightly differently here.

[ocornut]

I know for #19 I ended up figuring out that ImGuiTestContext::GetWindowTitlebarPoint was picking an invalid point on super small windows (had a note to report / investigate a fix later -- IIRC it looked like it was due to not avoiding the close/window menu buttons.), might just be the same issue manifesting its self slightly differently here.

Thanks for the PR. That’s worth investigating separately, perhaps with its own test. And I guess maybe that function should be GetWindowTitlebarPointForMoving.
Otherwise if we can make that function return a failure state, perhaps the higher-level users eg WindowMove() can decide to fallback to moving position directly using SetWindowPos(), although in principle ideally we’d try to steer the test engine toward behaving more like a real user.

[ocornut]

While we are here I suggest adding some basic sanity tests to check for the behavior of DockBuilderCopyDockSpace().
Which I guess would involve e.g. docking stuff in one dockspace, running copy and checking other dockspace.
Depending on amount of content we can rename this to docking_dockspace_copy to add a new test docking_dockspace_copy
and keep this one separate.