feat(config): Add --prune config option

[KochiyaOcean]

Closes #3906

As the ticket above says, the npm i command with --package-lock false option has changed its behavior since npm@7, which no longer prevents automatic pruning and currently there is no option to disable the automatic pruning process.

This pull requests add a new config option prune, when it's set to false, the automatic pruning will be disabled. With this option user will be able to install packages without getting the node_modules folder pruned.

Also the pull requests updated the description of package-lock option to match the current behavior of the config

[KochiyaOcean]

Rebased branch to resolve conflicts

[neutraali]

This would be very nice to have. Otherwise people running multiple npm install are stuck using npm@6 (as that version doesn't have aggressive pruning).

[neutraali]

Any progress on this? Would be really nice to get out from under npm@6...

[rommni]

I known this is a old issue but any news on it because I don't think there is an other solution for this ?

[nnfhhvbb]

。