runner: simplify integrity label handling

This removes set_integrity_label and merges it into alloc, alloc_obj.

We also change register_shared_variable so that it now allocates frames
with a sensible default label. This allows us to drop the manually set
labels from the built-in shared mem templates.

templates: specify connector label when allocating shared memory

This modifies register_shared_variable, etc. to accept a label argument
and updates shared memory templates to pass in the connector label.

As shared frame objects are now allocated under the correct labels,
we no longer need to fix them in object_label_mapping prior to the
integrity verification.

Modify shared regions to use AddrSpaceAllocator

This updates register_shared_variable to use AddrSpaceAllocator instead
of shmem. The relevant filter functions have also been removed.

Change Camkes alignment and section linking policy

There are now special sections created by the Camkes linker script that
are aligned to each of the architecture page sizes. Symbols that require
a certain alignment in order to be backed by an underlying seL4 frame of
a certain size should declare to be in the section of that size. The
purpose of this is to drastically simplify the linking policy shared
between Camkes and the capdl python scripts that would create the
address space objects.

The linker script requirement is because a compiler/assembler is not required to
respect the `align` attribute above a certain small size and any
alignment requirements on the order of page sizes needs to be specified
by a linker script.

These changes make it possible to remove some architecture special cases
that exist in Camkes templates, which is why they are removed.

It is assumed that any of the special policy associated with the special
section names: guarded, shared_*, ignore_* and persistent can still be
implemented by using the new section name with the same alignment, eg
align_12bit for all symbols that require 4k guard pages.

Make error-handler.c a macro

Moves the 'error-handler.c' template logic into a 'helpers' template as a macro with
arguments, instead of a template file that is 'include'd and relies on peeking at
global variables to simulate argument passing.

Fix licenses

Replaced seL4Asynch with seL4Notification

Breaking change that replaces the sel4Asynch* connectors with
corresponding seL4Notification* connectors.

Refactored parser init commit.

Renamed seL4Asynch connector to seL4Notification, keeping support for seL4Asynch