Implement AssertSuspension

[dhil]

This patch provides an implementation for the Wast assert_suspension directive, enabling us to run test cases that tests for unhandled suspensions.

[frank-emrich]

It seems like assert_suspension is a specialisation of assert_trap, is that correct? It asserts that a trap happens, but is more specific about which trap(s) should occur.

[dhil]

It seems like assert_suspension is a specialisation of assert_trap, is that correct? It asserts that a trap happens, but is more specific about which trap(s) should occur.

Yes, you can view it as a particular trap.