test: have inspector test pick an open port
This ensures that cctest can be ran concurrently with other instances of cctest or while the node is ran with --inspect.
Ref: https://github.com/nodejs/node/issues/10858
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
test, inspector - server now works with the port 0 and test leverages that.