simplify graph update

[aharon-abramson]

The suggested graph update mechanism seems computationally complex: an implementation has to traverse both the modifiable and executable graphs to identify any changes to either inputs or outputs.
I better like the OpenCL approach, where one directly updates a cl_mutable_command_khr handle. We can add an update method to class node. We can also add graph::get_node(size_t index) for obtaining the nodes created during queue recording.

[EwanC]

Hi Aharon, thanks for your input. The current draft update mechanism is aimed at library use cases, where an application creates an graphs from recording a library call, where they don't have access to SYCL objects like buffers/USM to update.

A more fine grained update mechanism is something we're definitely looking at adding for future versions of the spec, so will keep a design like this in mind.

[aharon-abramson]

Great, thanks.