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/system/pisysteminfo.cpp

@@ -207,7 +207,7 @@ PIVector<PISystemInfo::MountInfo> PISystemInfo::mountInfo(bool ignore_cache) {
 PIString confDir() {
 	return
 #ifdef WINDOWS
-#  ifndef PIP_NO_FILESYSTEM
+#  ifdef PIP_HAS_FILESYSTEM
 		PIDir::home().path() + "/AppData/Local"
 #  else
 		""
@@ -215,7 +215,7 @@ PIString confDir() {
 #elif defined(ANDROID)
 		""
 #else
-#  ifndef PIP_NO_FILESYSTEM
+#  ifdef PIP_HAS_FILESYSTEM
 		PIDir::home().path() + "/.config"
 #  else
 		""
@@ -242,7 +242,7 @@ PIString PISystemInfo::machineKey() {
 		PISystemInfo * si = instance();
 		PIByteArray salt;
 		PIString conf = confDir() + "/.pip_machine_salt";
-#ifndef PIP_NO_FILESYSTEM
+#ifdef PIP_HAS_FILESYSTEM
 		if (PIFile::isExists(conf)) salt = PIFile::readAll(conf);
 		if (salt.size_s() != SALT_SIZE) {
 			salt = generateSalt();