chore: support minimum node 20, use native node test runner

[filmaj]

playing around to see how hard this will be. seems to work pretty well! in prep for node 18 being EOL'ed in April.

• min node 20+; CI tests node 20, 22 and 24
• use native node --test runner, remove tape and any testing related dependencies

this approach is much faster on my macbook w/ node v20:

$ time npm run coverage
...
npm run coverage  1.40s user 0.27s system 239% cpu 0.696 total

compared to main:

➜ time npm run coverage
...
npm run coverage  4.11s user 0.75s system 87% cpu 5.526 total