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/main/io_utils/pistreampacker.h

@@ -24,7 +24,7 @@
 
 #ifndef PISTREAMPACKER_H
 #define PISTREAMPACKER_H
-#ifndef PIP_NO_SOCKET
+#ifdef PIP_HAS_SOCKET
 
 #include "piethutilbase.h"
 #include "piobject.h"
@@ -201,5 +201,5 @@ private:
 	mutable PIMutex prog_s_mutex, prog_r_mutex;
 };
 
-#endif // PIP_NO_SOCKET
+#endif // PIP_HAS_SOCKET
 #endif // PISTREAMPACKER_H