fix(help-search): use config.npmPath to find docs

[wraithgar]

Tests were also refactored to use real npm/docs

[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	33.662 ±0.58	16.973 ±0.00	14.886 ±0.09	17.460 ±0.76	2.669 ±0.00	2.657 ±0.01	2.185 ±0.06	10.564 ±0.04	2.155 ±0.03	3.081 ±0.02
#4920	34.530 ±2.00	16.935 ±0.21	15.186 ±0.22	17.574 ±0.91	2.747 ±0.13	2.673 ±0.03	2.168 ±0.01	10.533 ±0.03	2.152 ±0.02	3.200 ±0.13

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	26.591 ±0.04	12.748 ±0.07	11.244 ±0.09	12.078 ±0.62	2.430 ±0.04	2.432 ±0.02	2.159 ±0.02	7.692 ±0.15	2.029 ±0.02	2.756 ±0.03
#4920	24.982 ±0.28	12.721 ±0.00	11.170 ±0.07	12.090 ±0.51	2.443 ±0.01	2.417 ±0.03	2.132 ±0.01	7.671 ±0.07	2.019 ±0.00	2.737 ±0.00