core: Backport 'Implement wlr_foregin_toplevel_handle's fullscreen ma… #3356

Job	Run time
Test with GCC/musl/libstdc++/BFD on Alpine Linux	1m 52s
Test with clang/glibc/libc++/lld on Arch Linux	21m 28s
Check code style with uncrustify	1m 11s
	24m 31s

Provide feedback