Over the years a number of new bytecode optimisations have been added to
the compiler, and in some cases these have introduced issues with the
mapping of IPs from normal code to debug code that the debugger does when
translating a stack frame to a debug frame. The problems appear to be a
combination of incorrect management of the text maps in the compiler and
the Debugger's ip remapping not handling some corner cases that are either
new or have become more common. This work isn't finished yet, and hence
there are still two versions of the mapping method. One in use, one under
(incomplete) testing.

Revise STB to use a policy object to determine various aspects of the
format that have changed over time. This allows us to handle variability
when reading old versions in a more elegant manner, but more importantly
allows us to write in the old format. This only works if the class format
hasn't changed - we don't have the ability to write classes in old formats,
only to respect the overall STB format for particular versions. This does
however improve round-tripping with of packages between D7 and D8.

All of the existing conversions were visited, and the test coverage of old
versions improved where old binary serialisation data existed, or could be
recreated. Existing view/presenter tests not under PresenterTest were
moved there to be able to inherit the STB/STL conversion tests.