Reduce + recode images to JPEG if they are too huge (#3956)

I.e. > 500K for the balanced media quality and 130K for the worse one. This can remove animation and
transparency from PNG/WebP, but then a user always can send an image as a file.

Also don't reduce wide/high images if they aren't huge. Among other benefits, this way most of PNG
screenshots aren't touched.

Also remove Exif from all images, not from JPEGs only.

Author: iequidoo

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Check provider database with CI. #4099 
 - Switch to DEFERRED transactions #4100
 - Remove metadata from avatars and JPEG images before sending #4037
+- Reduce + recode images to JPEG if they are > 500K in size #4037
 
 ### Fixes
 - Do not block async task executor while decrypting the messages. #4079