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/thread/pithreadpoolworker.h

@@ -33,7 +33,7 @@
 //! \~\brief
 //! \~english Fixed-size pool of worker threads for generic-purpose tasks.
 //! \~russian Фиксированный пул рабочих потоков для задач общего назначения.
-#ifndef PIP_NO_THREADS
+#ifdef PIP_HAS_THREADS
 class PIP_EXPORT PIThreadPoolWorker: public PIObject {
 	PIOBJECT(PIThreadPoolWorker)
 
@@ -173,7 +173,7 @@ private:
 	PISet<PIObject *> contexts;
 	std::atomic_int64_t next_task_id = {0};
 };
-#endif // PIP_NO_THREADS
+#endif // PIP_HAS_THREADS
 
 
 #endif // PITHREADPOOLWORKER_H