Change metadata sync delay in ext renderer from float to int data type

In the external renderer, one can set a delay to be applied to the metadata input. This is quantized to 5ms steps (subframe size of TD renderer).

Currently, this value is read as a flaot value from the command line and only later quantized, so one has float values around all the time which can be principally of any value. As pre-quantizing makes BASOP implementation in a porting MR easier, I would propose to make this refactoring change on the float size already.