Remove TypeSystem.convert_from_binary() method and related code

- remove `TypeSystem.convert_from_binary()`
- remove `TypeSystem.get_type_size()` method
- remove `convert_binary()` function from `bytes` type module

This issue needs to be deferred for a several months until all usage of these routines is removed.
Usage examples:

- `TypeSystem.get_type_size()`: https://code.eng.archsys.io/search?q=get_type_size
- `TypeSystem.convert_from_binary()`: https://code.eng.archsys.io/search?q=convert_from_binary

There was a pull request created for this issue, it could be used later when it is time to commit the changes:
https://github.com/iotile/typedargs/pull/84