[FEATURE] ViewHelper to display file sizes

Simple ViewHelper that converts the size of a file to a human
readable string.

Usage:
{fileSize -> f:format.bytes()}

Change-Id: Iffb155e209fe0d2e89aae6d93706e994b4b0b8e7
Resolves: #49139
Related: #49128
Releases: 6.2
Reviewed-on: https://review.typo3.org/21436
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Zbigniew Jacko
Tested-by: Zbigniew Jacko
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn