Update counter example to be simpler and a better reference

[mkorbel1]

Description & Motivation

Some feedback about the counter example has been:

• For newcomers, it is a pretty verbose implementation.
• The example testbench code doesn't expose newcomers to the await style.

This PR updates the example to use some awaits as well as make the counter implementation simpler. The downside is that it no longer demonstrates Sequential in the more general case, but there are other examples and API docs that can be referenced for that.

Related Issue(s)

N/A

Testing

Example is covered by test, also rerun locally

Backwards-compatibility

Is this a breaking change that will not be backwards-compatible? If yes, how so?

No

Documentation

Does the change require any updates to documentation? If so, where? Are they included?

Basically just doc update