Revert "src, tools: add debug symbols for node internals"

This reverts commit 446c1ecf.

Reverted for breaking make test-v8. The "find all relevant system headers" logic in tools/gen-postmortem-metadata.py needs more work.

Also reverts commit e46c3f74. ("tools: fix typo in gen-postmortem-metadata.py".)

CI: https://ci.nodejs.org/job/node-test-pull-request/11662/ V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/1074/