src: Remove lttng support.

This cleans up and removes lttng support completely. Recent discussion
on a PR to deprecate lttng suggested that we remove it completely
pending feedback from the TSC.

This should be considered a non breaking change, as a recent PR reveals
that compiling with this system has been broken for nearly two years.

Refs: https://github.com/nodejs/node/issues/18971
Refs: https://github.com/nodejs/node/pull/18975
Refs: https://github.com/nodejs/node/pull/18945

PR-URL: https://github.com/nodejs/node/pull/18982


Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jackson Tian <shyvo1987@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>