Fix ARM tests and gate on new failures

[fw-immunant]

Currently (322e9db), the following tests fail on ARM:

• recursion (Fixed by Tag accesses to stack pointer TLS locations in call gates #462)
• simple1 (seems we don't tag accesses to a static)
• static_addr_taken (possibly the same issue)
• read_config (MTE violation inside PartitionAlloc)

We should fix these and make sure that future compartment violations show up as CI failures, possibly by altering our QEMU patch to only continue past the first violation if we opt in.

[ayrtonm]

This is probably the issue with simple1 #314 (comment)

[fw-immunant]

The read_config issue boils down to us allocating untagged memory in shared_malloc which should be accessible from any compartment, but the memory accesses within the implementation of shared_malloc (in PA itself) are still applying the x18 tag. We might be able to save/restore x18 around the implementation of our shared allocation APIs, but I think we would need per-compartment copies of every shared allocation entrypoint so that the compartment to return to gets encoded in control flow.

I'm also not sure what to do about regular accesses to shared allocations.