cpuinfo: Rename SDL_GetCPUCount to SDL_GetNumLogicalCPUCores

This was the only API that broke the "GetNumThings" convention
used elsewhere, so renaming it helps with consistency.
Adding "logical cores" to the name also makes it a bit
more immediately obvious what the count actually represents.

include/SDL3/SDL_oldnames.h

@@ -74,6 +74,7 @@
 #define SDL_NewAudioStream SDL_CreateAudioStream
 
 /* ##SDL_cpuinfo.h */
+#define SDL_GetCPUCount SDL_GetNumLogicalCPUCores
 #define SDL_SIMDGetAlignment SDL_GetSIMDAlignment
 
 /* ##SDL_endian.h */
@@ -703,6 +704,7 @@
 #define SDL_NewAudioStream SDL_NewAudioStream_renamed_SDL_CreateAudioStream
 
 /* ##SDL_cpuinfo.h */
+#define SDL_GetCPUCount SDL_GetCPUCount_renamed_SDL_GetNumLogicalCPUCores
 #define SDL_SIMDGetAlignment SDL_SIMDGetAlignment_renamed_SDL_GetSIMDAlignment
 
 /* ##SDL_endian.h */