fix: 100% coverage in tests

[wraithgar]

• Removed dead code in lib/utils/usage.js.
• Removed dead code in lib/base-command.js.
• Removed "load-all" test, we currently have 100% coverage and new PRs
  without tests will be rejected if they don't add coverage for new
  files.
• Removed check-coverage script as a separate command.
• Removed separate coverage test in ci.yml.
• Removed coverage flag from tap config, the default is already to
  enforce 100% coverage.

Added another commit that cleans up usage, which removing the dead code from base-command revealed as being needed.

• Removed usage lib, rolled logic into base-command.js
• Cleaned up usage output to be less redundant

[npm-robot]

found 1 benchmarks with statistically significant performance regressions

• app-large: no-clean:audit

timing results

app-large	clean	lock-only	cache-only	cache-only peer-deps	modules-only	no-lock	no-cache	no-modules	no-clean	no-clean audit
npm@8	54.614 ±2.72	36.328 ±0.73	22.541 ±0.57	25.401 ±1.45	3.528 ±0.05	3.611 ±0.00	2.925 ±0.09	14.539 ±0.01	2.855 ±0.03	3.980 ±0.02
#4607	56.995 ±0.58	36.619 ±0.05	22.444 ±0.53	26.387 ±0.83	3.681 ±0.02	3.749 ±0.11	2.924 ±0.02	15.505 ±0.31	2.969 ±0.06	4.521 ±0.31

app-medium	clean	lock-only	cache-only	cache-only peer-deps	modules-only	no-lock	no-cache	no-modules	no-clean	no-clean audit
npm@8	39.577 ±0.37	27.423 ±0.52	15.887 ±0.58	17.303 ±0.39	3.297 ±0.05	3.353 ±0.05	2.993 ±0.07	11.237 ±0.27	2.744 ±0.02	3.776 ±0.02
#4607	41.724 ±0.71	28.645 ±0.07	16.589 ±0.01	18.132 ±0.15	3.346 ±0.04	3.403 ±0.07	2.987 ±0.04	11.062 ±0.17	2.743 ±0.01	3.821 ±0.03