[3.12] gh-105704: Disallow square brackets (`[` and `]`) in domain names for parsed...

[3.12] gh-105704: Disallow square brackets (`[` and `]`) in domain names for parsed URLs (GH-129418) (GH-129527)

gh-105704: Disallow square brackets (`[` and `]`) in domain names for parsed URLs (GH-129418)

* gh-105704: Disallow square brackets ( and ) in domain names for parsed URLs

* Use Sphinx references

* Add mismatched bracket test cases, fix news format

* Add more test coverage for ports

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(cherry picked from commit d89a5f6a6e65511a5f6e0618c4c30a7aa5aba56a)

Co-authored-by: Seth Michael Larson <seth@python.org>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>