doc: tor.md updates (19961)
doc: tor.md updates (19961)

Summary:
> doc: update tor.md address examples from onion v2 to v3

> doc: add tor.md section on how to get tor info via bitcoind

> doc: update -externalip documentation in tor.md

This is a backport of [[https://github.com/bitcoin/bitcoin/pull/19961 | core#19961]]

Test Plan: proofreading

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11031

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