Deal with UUID for content sandbox temp folder on Windows and Mac

comment:56:ticket:16010 mentioned:

Very important side issue is that the sandboxing feature adds `security.sandbox.content.tempDirSuffix` pref which is a 128-bit GUID that allows to uniquely identify your copy of Tor Browser. It is persistent and leaves unique traces on every machine you use in system %TEMP% folder.

We should find a good way dealing with that. Maybe a first start is to set the pref, so that every Windows user has the same sandbox temp dir name.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information