Docs: static keyword

[anshumanmohan]

First steps towards documenting the shiny new static keyword.
Progress so far:

• Background about static vs dynamic.
• Intro to Calyx's support for static: components, groups, control.
• Information about the guarantees given to us by static.
• Removed the "tricks and tips" section.
• Examples.

[sampsyo]

Awesome; thanks for getting this going! This looks REALLY great!

I have put nothing in there about refinement; it's perhaps "just a cute detail" as far as the user is concerned. Thoughts?

I think it would be great to add something about this someday, but in a separate PR! Namely, a thing that users might want to know is the following paradigm for how they might use static:

1. Emit fully dynamic code everywhere.
2. Observe places where performance is suffering because static inference was incomplete.
3. Sprinkle static qualifiers in there.

The relevant idea offered by refinement is that step 3 is guaranteed not to break the program.

By this logic, I'd say that inference should be presented here, but I'm not sure about compaction. Thoughts?

Yep!! In particular, maybe we can talk about inference/promotion when we add stuff about refinement above. It's good for people to know this pass exists; the details of how it works or how capable it is probably are not worth writing down. Compaction seems like "just an optimization" like any other, i.e., it can be documented like any other optimization pass.

[anshumanmohan]

Thanks Adrian, your suggestions are now in #1885!

[anshumanmohan]

I have removed the section about guarantees and instead distributed that info where appropriate. This also means that we have one list of the various control operators, where I introduce each, give an example, and explain the associated guarantees. A little better than making a number of corresponding lists.

[rachitnigam]

LGTM! I like the list of control operators. One thing to consider is making them headings so that we can link to them more easily like with dynamic operators (example: invoke). Feel free to change and merge at your discretion modulo @sampsyo comments!

[anshumanmohan]

Nice, I made them into headings and also linked back to the dynamic variants in a number of places. Merging for now.