process: move DEP0062 (node --debug) to end-of-life

This has already been practically end-of-life since `node --debug`
alone would exit the process. This patch drops support of
`node --inspect --debug-brk` as well.

`node --inspect --debug-brk` has been deprecated since v8,
it has been maintained so that vendors can target Node.js
v6 and above without detecting versions.
The support of `--inspect`, which starts from v6, will reach
end-of-life in April 2019, it should be safe to drop the support
of `--inspect --debug-brk` altogether in v12.

Also removes `process._deprecatedDebugBrk`

PR-URL: https://github.com/nodejs/node/pull/25828
Refs: https://github.com/nodejs/node/pull/12949


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>