Blender Git Loki

Sanitize type 'size' parameters in our read/write file code

This patch tries to sanitize the types of our size parameters across our read
and write code, which is currently fairly inconsistent (using `int`, `uint`,
`size_t`...), by using `size_t` everywhere. Since in Blender file themselves
we can only store chunk of size `MAX_INT`, added some asserts to ensure that
as well.

See {T79561} for details.

Differential Revision: https://developer.blender.org/D8672