Use new simple I/O port interface

seL4: remove deleted arch_info function

seL4: Add new stdio platform support

A rumprun process may be initialised with existing stdio 'pipes' which
consist of circular buffers in shared memory and notification objects
for signalling the availability of data in the buffers.

Refactor custom_simple_vspace_bootstrap_frames

Make it more readable and easy to modify

Initialise timer and serial config

Do not rely on memory being 0'd

Remove hardware serial from seL4 rumprun platform

Instead, rely on being provided an endpoint to
contact a serial server on.
putc now buffers characters until the buffer is full, a
newline is printed or flush is explicitly called, at this point
it will IPC the serial server to print the contents of the buffer.

Use an ltimer backed by RPC instead of HW timer

Such that we can run multiple rump apps.

sel4 platform: use slots set up by sel4utils

processes created by sel4utils already have some initial caps in them.
Remove the slots in init data that duplicated these and use the
sel4utils function to get them in the simple implementation for
get_init_cap.

seL4: Add support for seL4 mcs kernel

seL4: Use new sel4platsupport timer API

seL4: run astyle over project

seL4: rename untyped_descriptor_t fields

seL4: Add CAmkES support

seL4: Reduce error output boilerplate

seL4: Change to use simple implementation