Add `PhysicsServer2/3D::space_step()` to step physics simulation manually #16778

Job	Run time
📊 Static checks / Code style, file formatting, and docs	30s
🍏 iOS / Template (target=template_release)	12m 31s
🍎 macOS / Editor (target=editor, tests=yes)	39m 24s
🏁 Windows / Editor (target=editor, tests=yes)	39m 31s
🍎 macOS / Template (target=template_release)	16m 48s
🏁 Windows / Template (target=template_release)	28m 31s
🤖 Android / Template (target=template_release)	27m 0s
🌐 Web / Template (target=template_release)	17m 54s
🐧 Linux / Editor w/ Mono (target=editor)	33m 36s
🐧 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)	35m 55s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	29m 40s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	25m 55s
🐧 Linux / Template w/ Mono (target=template_release)	22m 42s
🐧 Linux / Minimal template (target=template_release, everything disabled)	13m 6s
🪲 Godot CPP / Build and test Godot CPP	6m 52s
	5h 49m 55s

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