Cleanup: rename PIL to BLI

The term `PIL` stands for "platform independent library." It exists since the `Initial Revision`
commit from 2002. Nowadays, we generally just use the `BLI` (blenlib) prefix for such code
and the `PIL` prefix feels more confusing then useful. Therefore, this patch renames the
`PIL` to `BLI`.

Pull Request: https://projects.blender.org/blender/blender/pulls/117325

source/blender/editors/interface/interface_panel.cc

@@ -16,9 +16,8 @@
 
 #include "MEM_guardedalloc.h"
 
-#include "PIL_time.h"
-
 #include "BLI_blenlib.h"
+#include "BLI_time.h"
 #include "BLI_utildefines.h"
 
 #include "BLT_translation.h"
@@ -1792,7 +1791,7 @@ static void ui_do_animate(bContext *C, Panel *panel)
   uiHandlePanelData *data = static_cast<uiHandlePanelData *>(panel->activedata);
   ARegion *region = CTX_wm_region(C);
 
-  float fac = (PIL_check_seconds_timer() - data->starttime) / ANIMATION_TIME;
+  float fac = (BLI_check_seconds_timer() - data->starttime) / ANIMATION_TIME;
   fac = min_ff(sqrtf(fac), 1.0f);
 
   if (uiAlignPanelStep(region, fac, false)) {
@@ -2650,7 +2649,7 @@ static void panel_handle_data_ensure(const bContext *C,
   data->startofsy = panel->ofsy;
   data->start_cur_xmin = region->v2d.cur.xmin;
   data->start_cur_ymin = region->v2d.cur.ymin;
-  data->starttime = PIL_check_seconds_timer();
+  data->starttime = BLI_check_seconds_timer();
 }
 
 /**