Spring fix:Spring fails to determine XML is XSD-based if DOCTYPE appears in a comment

It solves the problem that XmlValidationModeDetector cannot determine whether XML is based on XSD due to improper parsing of comments spanning multiple lines in the original XML configuration file.

Fixes #27915

Comment From: pivotal-cla

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Comment From: pivotal-cla

@shooye Thank you for signing the Contributor License Agreement!

Comment From: sbrannen

Hi @shooye,

We really appreciate all the effort you put in to provide a fix!

In the end, we decided to go with a simpler solution that relies on recursion in order to reuse the existing comment parsing logic. If you're interested in checking it out, you'll find it in https://github.com/spring-projects/spring-framework/commit/4b1b25496bfd72c288c3af07c741183d0d90567a#diff-d2b71d5dbef74357add917ba7662a8f3d376fe9e965f82cd08407587b55bf833.

In light of that, I am closing this PR.

Thanks again for reporting this set of bugs.