tools (common/utils): new methods to parse and generate file size with symbols: - `parseSize` lets parse a size which can be either a int, or a string with a symbol like `Mio` - `getSizeMultiplier` returns a tuple of size with it's multiplier symbol - `getHumanSize` returns a string with size and adapted multiplier.

these certificates are used for demo purpose only. Those must be the same as in
backend_e2e (they are generated there)