lib: end-of-life the deprecated require('sys')
See: https://github.com/nodejs/node/pull/2405
It looks like this was going to be considered for Node.js 6.x, so now that 12.x is upcoming, maybe we are ready?
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines