filesystem: Added SDL_GetCurrentDirectory(). #2760

Job	Run time
Create test plan	9s
level1 / Haiku	2m 0s
level2 / Windows (MSVC, x86)	4m 1s
level2 / Windows (MSVC, ARM64)	2m 35s
level2 / FreeBSD	2m 43s
level2 / Windows (msys2, clang64)	5m 42s
level2 / RISC OS	1m 20s
level2 / Sony PlayStation Vita (GLES w/ pib)	3m 11s
level2 / Windows (MSVC, clang-cl x86)	5m 33s
level2 / Windows (msys2, mingw32)	8m 17s
level2 / Windows (MSVC, ARM)	3m 12s
level2 / Ubuntu 22.04	4m 30s
level2 / Windows (MSVC, x64)	5m 14s
level2 / tvOS (CMake & xcode)	1m 44s
level2 / Ubuntu 20.04 (Intel Compiler)	4m 46s
level2 / MacOS (Framework) (x64)	4m 54s
level2 / Android (CMake)	2m 48s
level2 / iOS (CMake & xcode)	2m 10s
level2 / LoongArch64	2m 43s
level2 / Android (Android.mk)	1m 7s
level2 / Android (CMake, lean)	2m 57s
level2 / Sony PlayStation Vita (GLES w/ PVR_PSP2)	3m 19s
level2 / Android (Gradle)	1m 57s
level2 / Sony PlayStation Portable	3m 45s
level2 / GDK (MSVC, x64)	1m 34s
level2 / Windows (msys2, mingw64)	8m 4s
level2 / Steam Linux Runtime (Sniper)	3m 3s
level2 / MacOS (GNU prefix)	3m 50s
level2 / Ubuntu 20.04 (Intel oneAPI)	6m 53s
level2 / NetBSD	2m 36s
level2 / Nintendo 3DS	1m 59s
level2 / MacOS (Framework) (arm64)	2m 12s
level2 / PowerPC	1m 53s
level2 / Windows (MSVC, clang-cl x64)	3m 45s
level2 / PowerPC64	1m 56s
level2 / Windows (msys2, ucrt64)	8m 13s
level2 / Sony PlayStation 2	5m 0s
level2 / Ubuntu 20.04	3m 56s
level2 / Windows (msys2, clang32)	6m 41s
level2 / Emscripten	9m 15s
	2h 31m 27s

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