Memory limit hit getting mime type / Gif upload broken

We have been getting OOM messages from finfo calls that get the mime type from a file buffer. See #1120 (closed) for full details.

This MR touches a number of different API endpoints for fetching and also changes the S3 Service write method so affects any media file upload.

/api/fs/v1/avatars

/api/fs/v1/banners

/api/fs/v1/paywall

/api/fs/v1/thumbnail <- This was producing the most errors given the number of times it gets hit

Some steps for reproduction:

1. Try to post a media file that exceeds 13M in size to the nesfeed.
2. POST /api/v1/media request will return a 200 OK status with Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 146703512 bytes) in /var/www/Minds/engine/Core/Storage/Services/S3.php on line 67 as the response

When this gets to staging, accessing the following URL should be successful, currently fails in production: https://www.minds.com/fs/v1/thumbnail/1026508015016828928/xlarge