util: remove custom inspection function
This removes the deprecated custom inspection function and fixes all tests accordingly.
Refs: https://github.com/nodejs/node/issues/15549
I guess we could merge #20525 first and land this one right afterwards.
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