Change parser to new Structural Pattern Matching Spec

[Vlek]

Brand new PEP 634 -- Structural Pattern Matching specification came out that may make pyparsing unnecessary and so that we can use the Python standard library for our parsing needs.

Pros:

• Offers a way to remove yet another dependency which reduces the potential for issues down the line if pyparsing does not get updates, both in terms of functionality and also malicious code threats.
• Potentially faster as we will not have to import outside code.
• Reduces overall footprint of the project on user's computers.

Cons:

• Requires yet another rewrite of underlying parser logic. The third time is the charm, but it's going to be even more of a pain now that additional features have been incorporated.
• Available starting at Python v3.10. This means that this spec is going to be out of reach of our general target audience for quite some time as we are currently shooting for 3.6-3.8. Ubuntu doesn't even have 3.9 officially yet.

[Vlek]

One way that we might be able to get around the 3.10 not being officially released issue is to use docker containers, but it's a pretty roundabout way of dealing with it: https://andrewlock.net/packaging-cli-programs-into-docker-images-to-avoid-dependency-hell/

The other option is to somehow, maybe Makefile, state that a virtual environment should be created that is a 3.10 version, like using asdf: https://stackoverflow.com/questions/2547554/multiple-python-versions-on-the-same-machine/46258340#46258340

[Vlek]

3.10 is now out and available. Still definitely not widely used, but is doable.