feat: add gnoffee PoC

[moul]

I'm pondering a few things about our setup:

1. Where's the best spot for the package: misc/, gnovm/, new top-level namespace, or its own repo?
2. Should this be a standalone command or a part of gno?
3. Right now, the command processes .gnoffee files and gives us output. You can see it on screen or save it using -w. But here's the twist: it currently blends the new bits with all the .gnoffee scripts, creating a full .go file. Another idea is to just pinpoint and add what's missing, resulting in a gnoffee.gen.go file. I'm weighing up both approaches and would appreciate your insights.

Any feedback or even a chat about it would be great. cc @gnolang/tech-staff @gnolang/core-contributors

Suggestion for reviewers: checkout the txtar tests: https://github.com/gnolang/gno/pull/1092/files#diff-a9299fce0ae91a6a0eb6e0bfc51ab83a51116d452703e4c82f473f1e933dff4f

Addresses gnolang/hackerspace#22
Addresses #1075
Depends on #1093 (tests fail on go1.19)

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[moul]

A next step would be to add support for *int128,256

[moul]

Will continue here -> gnoverse/gnoffee#1