src: refine maps parsing for large pages

Multiple sections may be marked as "r-xp" and with the executable's
path. We use the location of the `__nodetext` symbol added by the linker
script to ensure that the range we retrieve from the maps file does
indeed contain the Node.js text section.

Thanks to Suresh Srinivas <suresh.srinivas@intel.com>!

PR-URL: https://github.com/nodejs/node/pull/29973


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>