[client,sdl] Always disable decorations in multimon session

[caseif]

This pull request modifies the code responsible for enabling/disabling borders on FreeRDP windows to consider whether the current session is multimonitor. IMO it doesn't really make sense for a multimonitor session to have borders, and removing the effective requirement that window decorations be explicitly disabled in this case makes for a nicer experience.

Additionally, this code was causing my graphics driver to sometimes hang when initially opening the windows, I would assume due to the combination of SDL_WINDOW_BORDERLESS and SDL_SetWindowBordered(SDL_TRUE). As far as I can tell this is a bug in KWin 6, but removing this trigger is also nice.

[freerdp-bot]

Can one of the admins verify this patch?

[github-actions]

clang-tidy made some suggestions

[github-actions]

clang-tidy made some suggestions

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[akallabeth]

Sorry, you missed a case ;)

there is the exit fullscreen key combination, then it makes sense for multimonitor sessions to have decorations.

[caseif]

Would it be sufficient to handle this case by updating the borders when the fullscreen state changes? Also, is it strictly necessary that the borders be updated for all window events? If not it may simplify things to move this code to sdl_create_windows since presumably the other settings won't be changing after window creation, but I'm not sure whether any target platforms mess with window decorations in other cases.