refactor: rename PIP_NO_\* to PIP_HAS_\* with inverted logic

All feature flags now use positive naming (enabled by default):
- PIP_HAS_FILESYSTEM, PIP_HAS_THREADS, PIP_HAS_SOCKET
- PIP_HAS_PROCESS, PIP_HAS_DYNLIB, PIP_HAS_FFT, PIP_HAS_SERIAL

Preprocessor guards inverted:
- #ifndef PIP_NO_X → #ifdef PIP_HAS_X
- #ifdef PIP_NO_X → #ifndef PIP_HAS_X

CMake options default ON instead of OFF.
Platform blocks set flags OFF to disable features.

85 files transformed via Python script + 2 manual fixes.

libs/io_utils/pistreampacker.cpp

@@ -26,7 +26,7 @@
 #include "piiodevice.h"
 #include "pitranslator.h"
 
-#ifndef PIP_NO_SOCKET
+#ifdef PIP_HAS_SOCKET
 #ifdef __GNUC__
 #  pragma GCC diagnostic pop
 #endif
@@ -178,4 +178,4 @@ uint PIStreamPacker::sizeCryptedSize() {
 	return sizeof(int) + (crypt_size ? cryptSizeAddition() : 0);
 }
 
-#endif // PIP_NO_SOCKET
+#endif // PIP_HAS_SOCKET