Replace request with node-fetch

[sntran]

Even though request is one of the optionalDepedencies, it is still installed through normal npm install, and not many people will remember to use the --no-optional flag.

I did a search and request is only used in lib/less-node/url-file-manager.js. In that case, it's probably leaner to switch to something like node-fetch. request is 3.84MB installed while node-fetch is only 153KB installed.

I would be happy to create a PR for it if it's worth considering.

[jburson]

Also, request generates warnings for all consumers:
warning less > request@2.88.2: request has been deprecated, see request/request#3142

[matthew-dean]

This has been replaced with native-request via this PR: #3501