src: find .text section using dl_iterate_phdr

Use `dl_iterate_phdr(3)` to find the mapping containing
`__node_text_start` instead of parsing `/proc/self/maps`.

Signed-off-by: Gabriel Schulhof <gabriel.schulhof@intel.com>
Co-Authored-By: Ben Noordhuis <info@bnoordhuis.nl>
PR-URL: https://github.com/nodejs/node/pull/32244


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