Support synchronously printing special map types

[danobi]

Is your feature request related to a problem? Please describe.

It would be nice to be able to do:

BEGIN { @ = count(); printf("val: %d\n", count()) }

As a workaround, users can currently asynchronously do:

BEGIN { @ = count(); print(("val", @)) }

Describe the solution you'd like

Now that we can loop over map elements, we can codegen direct accesses to count() (and possibly others) and generate a value in-kernel. This makes the special map types a bit more usable.

Describe alternative solutions or features you've considered

Allow async printf(). But that breaks some existing contracts in docs.

[danobi]

Dup of #3126