DSS-2437, DSS-2438: Simplify native pdf drawer

Created by: bnazare

This PR addresses the issues raised in both DSS-2437 and DSS-2438. It then goes further and removes a lot of redundant calculations in SignatureFieldDimensionAndPositionBuilder.

The last commit of the bunch moves some code from SignatureFieldDimensionAndPosition into SignatureFieldDimensionAndPositionBuilder. At this point, that code was only being set up and called by SignatureFieldDimensionAndPositionBuilder and so I felt its purpose was being obfuscated by keeping it where it was. This is however a non-essential change so feel free to ignore that particular commit if you feel it is an overreach.