Add seL4DTBHW connector

This connector variant is similar to seL4DTBHardware, but takes a
hardware component on the From end.

Add seL4DMASharedData connector

This connector sets up a dataport connector that is added to the DMA
pool that the camkes runtime tracks for each component. Only one end of
the connection is expected to control allocating and freeing the memory,
the other ends can only perform cache operations and get the physical
addresses.

templates: Add seL4InitHardware template

This new template allows the user to provide DTB paths to device nodes
that CAmkES will try to initialise with drivers registered as driver
modules. This template is intended to be used with the interface
registration service in libplatsupport (util_libs) and libsel4camkes (in
this repo).

templates: Use one template for seL4SharedData

Dataport connectors don't typically have directionality and the template
is almost identical for each end of the connector.

Delete seL4RPC connector

Usages of this connector need to be replaced with seL4RPCCall. seL4RPC
was originally used for connections where the endpoint capabilities
couldn't have grant rights. Now that the seL4RPCCall connector supports
this and so this connector is not needed.

Remove seL4RPCSimple connector

Usages of this connector can be replaced with seL4RPCCall. The connector
is removed as seL4RPCCall should be used instead.

ast,runner: Remove template field from connector

This allows us to more easily extend the mechanisms for constructing
components and connectors.