Add a perf timing/stack module and start using it to diagnose PSP hitching

New src/dusk/perf module: a simple push/pop tick-stack (perfPush/perfPop/
perfReport) for measuring how long a labeled span of code takes, wired
into engine.c's init/dispose. perfGetTick() is a placeholder - real time
on DUSK_LINUX (clock_gettime) and DUSK_PSP (sceKernelGetSystemTimeWide),
0 elsewhere until a proper cross-platform answer is settled on.

Used it this session to chase a reported PSP hitch when crossing a chunk
boundary. Confirmed mapPositionSet itself (unload/load sweeps, chunk
order rebuild, entity chunkIndex recompute) is consistently under ~3ms -
not the cause. Along the way, found and fixed a real, unrelated bug:
logDebug()/logError() on PSP did a fopen+write+fclose to the Memory
Stick on every single call, which was massively inflating any perf
measurement that logged from inside another measurement (the actual
source of the ~29-128ms numbers first seen). That's now gated behind a
new DUSK_PSP_LOG_FILE CMake option (default off).

Also, as a real test based on this session's findings:
- MAP_CHUNK_LOAD_CONCURRENCY dropped from 2 to 1 (8 and 4 both crashed/
  were untested further on real PSP hardware; 1 is confirmed safe).
- MAP_CHUNK_LOAD_DELAY_TEST: an intentionally exaggerated (now 50ms)
  artificial delay between starting successive chunk loads, gated in
  mapChunkLoadNext/mapUpdate, to observe the effect on framerate.

All perf instrumentation call sites added during this investigation
(assetChunkLoaderSync, assetMeshLoaderSync, mapPositionSet, the map area
callback invocation, engine.c's frame boundary) were removed again once
they'd served their purpose - only the reusable perf module itself and
the two real fixes above remain.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/duskpsp/log/log.c

@@ -17,14 +17,17 @@ void logDebug(const char_t *message, ...) {
   vprintf(message, copy);
   va_end(copy);
 
-  // print to file
-  FILE *file = fopen("ms0:/PSP/GAME/Dusk/debug.log", "a");
-  if(file) {
-      va_copy(copy, args);
-      vfprintf(file, message, copy);
-      va_end(copy);
-      fclose(file);
-  }
+  #ifdef DUSK_PSP_LOG_FILE
+    // print to file - fopen+fclose every call is real, measured Memory
+    // Stick I/O cost (this is why the flag exists - see psp.cmake).
+    FILE *file = fopen("ms0:/PSP/GAME/Dusk/debug.log", "a");
+    if(file) {
+        va_copy(copy, args);
+        vfprintf(file, message, copy);
+        va_end(copy);
+        fclose(file);
+    }
+  #endif
 
   va_end(args);
 }
@@ -39,14 +42,17 @@ void logError(const char_t *message, ...) {
   vfprintf(stderr, message, copy);
   va_end(copy);
 
-  // print to file
-  FILE *file = fopen("ms0:/PSP/GAME/Dusk/error.log", "a");
-  if(file) {
-      va_copy(copy, args);
-      vfprintf(file, message, copy);
-      va_end(copy);
-      fclose(file);
-  }
+  #ifdef DUSK_PSP_LOG_FILE
+    // print to file - fopen+fclose every call is real, measured Memory
+    // Stick I/O cost (this is why the flag exists - see psp.cmake).
+    FILE *file = fopen("ms0:/PSP/GAME/Dusk/error.log", "a");
+    if(file) {
+        va_copy(copy, args);
+        vfprintf(file, message, copy);
+        va_end(copy);
+        fclose(file);
+    }
+  #endif
 
   va_end(args);
 }