tools: use built-in padStart instead of padString
This commit uses the built-in String.prototype.padStart
function instead of a helper function and thus gets rid of it.
CI: https://ci.nodejs.org/job/node-test-linter/13676/
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
commit message follows commit guidelines
Affected core subsystem(s)
tools