Fix XmlDeserializer when XML uses same tag in nested elements (#2339)

* Fix XmlDeserializer to use Elements() instead of Descendants() for nested XML

* Fix XmlDeserializer nested element bugs

- Fix Bug #1: HandleListDerivative now uses Elements() on containers instead of Descendants()
- Fix Bug #2: Deserialize RootElement selection prefers shallowest match
- Fix Bug #3: RemoveNamespace filters null values
- Add comprehensive tests for all three fixes

* Implement Qodo suggestion and simplify the fallback logic

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Co-authored-by: Copilot <[email protected]>

Merge remote-tracking branch 'origin/dev' into dev

Allow tabs in header value, fixes #2263

Don't allow CRLF in headers (#2258)

Added extensions for getting content header values (#2247)

Header value null check (#2241)

* Throw an exception when adding a header with `null` value
* Add multiple header values properly
* Default headers should allow multiple values

Syntax fix

Fix the XML docs

fix-auth (#2206)

* Add tests to OAuth1 signature and revert accidental authenticator renames

* Fix wrong timeout endpoint

Moved the changelog