Restore old namespace reconciliation behaviour

The xmlDOMWrapReconcileNamespaces method we used to fix the namespace
corruption issues in 8.1.21/8.2.8 caused regressions.
Primarily,

Restore old namespace reconciliation behaviour

The xmlDOMWrapReconcileNamespaces method we used to fix the namespace
corruption issues in 8.1.21/8.2.8 caused regressions.
Primarily, there is a similar corruption that the xmlReconciliateNs method
used to have in which a namespace is suddenly shifted
(SAML-Toolkits/php-saml#562) and the side-effect of removing redundant
namespaces causes problems when a specific serialization is required.

Closes GH-12308.

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Fix bug #55294 and #47530 and #47847: namespace reconciliation issues

We'll use the DOM wrapper version of libxml2 instead of the regular one.
It's conforming to the behaviour we expect

Fix bug #55294 and #47530 and #47847: namespace reconciliation issues

We'll use the DOM wrapper version of libxml2 instead of the regular one.
It's conforming to the behaviour we expect of DOM.
Most of this patch is tests.

I based and extended the tests on the code attached with the aforementioned
bug reports. Therefore the credits for the tests:
Co-authored-by: hilse at web dot de
Co-authored-by: robin2008 at altruists dot org
Co-authored-by: sgunderson at bigfoot dot com

We'll also change the searching point of the internal reconciliation to
start at the top of the added tree to avoid redundant work now that the
function is changed.

Closes GH-11454.

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