Improve limit for single s3 put uploads

[juliusknorr]

Follow up to #27877 to further address the comments from @kesselb

Could we use a higher value for single put operations? Like 25 or 50 MB. I understand the buffer uses the memory hence we should not pick a value to high. However most pictures have more than 5 MB nowadays.

100 MB was picked as the default, as per AWS S3 recommendation to make use of multipart upload for files larger than that:

In general, when your object size reaches 100 MB, you should consider using multipart uploads instead of uploading the object in a single operation.

https://docs.aws.amazon.com/AmazonS3/latest/userguide/mpuoverview.html

Memory overhead is the actual file size which would fit our recommended php memory limit of 512 MB still fairly easy.

[CarlSchwan]

Unused, it seems

[artonge]

Some php-cs warnings, else, looks good.

[juliusknorr]

Failure unrelated