Add support for launching the Play window in PiP mode #489

Job	Run time
📊 Static checks / Code style, file formatting, and docs	1m 11s
🤖 Android / Editor (target=editor)	24m 40s
🍏 iOS / Template (target=template_release)	14m 37s
🍎 macOS / Editor (target=editor, tests=yes)	31m 41s
🤖 Android / Template arm32 (target=template_release, arch=arm32)	17m 16s
🍎 macOS / Template (target=template_release)	20m 51s
🤖 Android / Template arm64 (target=template_release, arch=arm64)	17m 11s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	25m 59s
🐧 Linux / Editor w/ Mono (target=editor)	40m 15s
🌐 Web / Template w/o threads (target=template_release, threads=no)	26m 45s
🏁 Windows / Editor (target=editor, tests=yes)	49m 30s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, tests=yes, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=gold)	46m 52s
🏁 Windows / Template (target=template_release)	36m 22s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	35m 41s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	32m 34s
🐧 Linux / Template w/ Mono (target=template_release)	27m 11s
🐧 Linux / Minimal template (target=template_release, everything disabled)	15m 0s
🪲 Godot CPP / Build and test Godot CPP	8m 21s
	7h 51m 57s

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