wasm_sdk: use context, enable and use interrupts (#3211)

* wasm_sdk: use context, enable and use interrupts

All in all, there's three cases where cancellation is somewhat interesting:

- native functions: numbers.range
- host functions using topdown.Cancel: net.cidr_expand
- host functions using context.Context: http.send

The tests also pin down the behaviour of these three cases in topdown eval.
There, the numbers.range and net.cidr_expand cases _should_ be the same,
but as it turns out, the former didn't check for cancellation.

This is also fixed here.

The comparison of the wasmtime.Trap's Message() using strings.HasPrefix
is not great, but gets the job done for now.

If you see this in your test run,

    === RUN   TestEvalWithContextTimeout/wasm/net.cidr_expand
        rego_wasmtarget_test.go:209: failed checking error, got context deadline exceeded (context.deadlineExceededError)

we have not been able to acquire a VM from the pool within the deadline
of the context. It's been increased to 1s to make this not the reason
for test failures in github actions.

However, the test time for the rego package got inflated a bit now:

    github.com/open-policy-agent/opa/rego	8.764s	coverage: 75.8% of statements

----

There is some inherent race condition here: the context could be cancelled
when the Eval() function has already stopped calling into the VM. We then
set a trap, and the next call into the wasm instance will be interrupted.
To avoid that, we're "clearing interrupts" at the beginning of every call
path that leads into one or more wasm instance function calls. This is a
price to pay, but I couldn't find any robust solution to avoid the
problematic scenario.


* deps: revendor

This is for leaktest.

Signed-off-by: Stephan Renatus <stephan.renatus@gmail.com>