docs: consolidate docs and help for package spec

[wraithgar]

Many of our commands parse their args via
npm-package-arg, which is a good
standard way of parsing a "package" argument. However the docs
surrounding these args are not very consistent. This can lead to
confusion in commands such as npm publish where the behavior is
slightly different than in the past due to this.

This adds a new help command npm help package-spec that describes what
this argument is, and can be, and also updates all the commands that
interpret their args this with to refer to them as <package-spec>. It
also adds a link to the new help page on their docs pages.

[npm-cli-bot]

no statistically significant performance changes detected

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	38.852 ±1.31	20.886 ±0.08	18.701 ±0.11	21.449 ±0.55	3.382 ±0.04	3.315 ±0.02	2.755 ±0.14	13.058 ±0.09	2.621 ±0.02	3.733 ±0.02
#5048	38.830 ±1.13	20.742 ±0.47	19.332 ±0.19	23.073 ±0.01	3.422 ±0.09	3.410 ±0.02	2.778 ±0.00	13.386 ±0.01	2.760 ±0.02	4.107 ±0.16

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	28.165 ±1.15	15.397 ±0.13	13.864 ±0.17	14.760 ±0.16	3.024 ±0.03	3.021 ±0.10	2.800 ±0.13	9.500 ±0.10	2.489 ±0.04	3.383 ±0.00
#5048	28.451 ±1.40	16.066 ±0.10	13.744 ±0.31	15.335 ±0.40	3.102 ±0.01	3.052 ±0.00	2.742 ±0.07	9.556 ±0.15	2.537 ±0.05	3.440 ±0.00

[wraithgar]

Closes #4126

[fritzy]

When I run help on this branch, it doesn't match the response properly.

different approach later