Do not suppress EOFError/KeyboardInterrupt when standalone is disabled

[atugushev]

Raise Abort() exception in a chain with the original exception.

• fixes Unable to see EOFError exception in the traceback with disabled standalone mode #2379

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.

[atugushev]

Thanks!