GeezerVison

Script changes preparatory to introducing modules (in the layout we
found to work in VSJ4).

This allows us to test creation of the several kinds of Javadoc
publication.

We approximate the package structure we need for safe type system
construction and control of visibility developed in the VSJ prototype.
We reduce the breakage this causes by temporarily making some things
public (opposite to the goal).

This is a batch of changed and new files supporting the re-worked type
system. It is not a consistent state, so don't test it.

The core types have evolved with the type system. These changed and new
files relate to that. It is not a consistent state, so don't test it.

Exceptions have changed to be more like their implementation in CPython.
They cannot all be distinct Java types because of the need for
class-assignment, but some can.

We add/update descriptors and exposure mechanisms that have not already
slipped through, and a two actual modules. Many classes lack their full
set of features.

This is not yet a coherent state we can test.

We commit support for 3.11 byte code. Developing support for JVM byte
code leads to some refactoring of these classes.

This is the last of the core runtime code, so we include some updated
tests. The test suite as a whole should not be expected to pass on this
commit.

We update the existing tests to match changes in the core. We have some
tests still to add.

The test suite as a whole (as currently committed) ought to pass.

The type system springs into existence when needed. We have a battery of
tests to check that it does so in full working order, irrespective of
the trigger (even concurrent and re-entrant triggers).

Type attribute access is not correctly synchronised yet, so it's a
mystery that this test doesn't fail.

As well the files git merge cannot merge, some classes have moved and
other features (exceptions for example) have changed. We address those
changes during the merge.