This changeset attempts to breach into the implementation design of OutputSlot
(while largely retaining the API and the »Output Slot Protocol«).
While the actual problem that brought me to this point can be traced back to some
rather obvious mistake, namely to conflate the `BufferProvider` used as
backing implementation with a `BufferProvider` used as front-end API,
creating the new connections to use an `OutputBufferProxy` unveils some
further long-standing structural mismatch; notably this leads to the
difficulties to get the lifecylce management of `OutputSlot` and `DataSink`
under control.
So I remove one entire level from the implementation,
in a bold move to realign the design with the prospective usage pattern.
Obviously, this breaks a lot of further code, and I need to rewire
the Allocation implementation altogether, and provide a new functor based
implementation for `DataSink`
The old implementation of `DiagnosticOutputSlot` is now disabled
and will be re-written from scratch, and no longer tangled to `BufferProvider`
- `OutputManager` remains in Steam-Layer for now
- the `Timings` and `OutputSlot` are now a self-contained
These are generic vehicles to verify computation structures.
Since they are in no way related to our models, they belong into »Vault« layer
Furthermore this reorganisation of test support components is prerequisite
to also move further generic facilities down into the Vault
