osxbundle: fix slow and wasteful memory allocation

when using the bundle with activated big enough cache, very slow and
wasteful memory allocations lead to jittery playback and lot of dropped
frames. the cache had to have a certain size so it would constantly
allocate new memory to reproduce this. this never happens when started
from the terminal.

the source of the problem is a different malloc allocation policy,
MALLOC_NANO, that allocated a huge amount of virtual memory without
actually using it. the usage was between 0% to 25% of that virtual
memory. the binaries allocation policy on the other hand used >80% of
that allocated virtual memory and was a lot more efficient, it would use
MALLOC_TINY instead.

this is fixed by setting the MallocNanoZone environment variable to 0
to use the V1 of the allocation policy. when started from the bundle via
launchd this is forced to 1 and V2 policy which causes this problem.

some more info can be found in following file and its comments on the
Apple open source site:
https://opensource.apple.com/source/libmalloc/libmalloc-317.40.8/src/nano_malloc_common.c.auto.html

Fixes #7405

TOOLS/osxbundle/mpv.app/Contents/Info.plist

@@ -188,6 +188,11 @@
     <string>${VERSION}</string>
     <key>NSHighResolutionCapable</key>
     <true/>
+    <key>LSEnvironment</key>
+    <dict>
+      <key>MallocNanoZone</key>
+      <string>0</string>
+    </dict>
     <key>CFBundleURLTypes</key>
     <array>
       <dict>