Make AudioStreamPlayer's `get_playback_position` more accurate #113

Job	Run time
📊 Static checks / Code style, file formatting, and docs	3m 27s
🍎 macOS / Editor (target=editor, tests=yes)	4m 36s
🍏 iOS / Template (target=template_release)	2m 23s
🤖 Android / Template (target=template_release)	3m 54s
🐧 Linux / Editor w/ Mono (target=editor)	5m 5s
🐧 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)	15m 51s
🍎 macOS / Template (target=template_release)	4m 7s
🌐 Web / Template (target=template_release)	1m 26s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	7m 25s
🏁 Windows / Editor (target=editor, tests=yes)	11m 15s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	10m 59s
🏁 Windows / Template (target=template_release)	5m 49s
🐧 Linux / Template w/ Mono (target=template_release)	2m 35s
🐧 Linux / Minimal template (target=template_release, everything disabled)	2m 1s
🪲 Godot CPP / Build and test Godot CPP	11m 24s
	1h 32m 17s

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