Revert "gpu: replace f32.Point/Rectangle with image.Point/Rectangle"

This reverts commit 36a2fa37c7.

Reason is that text rendering broke on some Android devices[0].

[0] https://lists.sr.ht/~eliasnaur/gio/%3CPH7PR02MB1003858FA1B27C8A53BE96815DDA1A@PH7PR02MB10038.namprd02.prod.outlook.com%3E

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/caches.go

@@ -4,7 +4,8 @@ package gpu
 
 import (
 	"fmt"
-	"image"
+
+	"gioui.org/internal/f32"
 )
 
 type textureCacheKey struct {
@@ -35,7 +36,7 @@ type opCache struct {
 type opCacheValue struct {
 	data pathData
 
-	bounds image.Rectangle
+	bounds f32.Rectangle
 	// the fields below are handled by opCache
 	key  opKey
 	keep bool