inspector: implement --cpu-prof-interval

This patch implements --cpu-prof-interval to specify the sampling
interval of the CPU profiler started by --cpu-prof from the command
line. Also adjust the interval to 100 in test-cpu-prof.js to make
the test less flaky - it would fail if the time taken to finish
the workload is smaller than the sampling interval, which was
more likely on powerful machines when the interval was 1000.

PR-URL: https://github.com/nodejs/node/pull/27535


Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>