[backport#17304 11/18] Refactor: Move GetMetadata code out of getaddressinfo

Summary:
Easier to review ignoring whitespace:

git log -p -n1 -w

This commit does not change behavior.

https://github.com/bitcoin/bitcoin/pull/17304/commits/a18edd7b383d667b15b6d4b87aa3a055a9fa5051

Depends on D7157

Partial backport of Core PR17304

Test Plan:

ninja check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7158