Stop XML word selection at punctuation and camel case

[mvanhorn]

LLMs, Commit messages and PR description:

xmlIdentifierAcceptor now accepts only characters for which Character.isJavaIdentifierPart is true, which keeps letters, digits, and underscore in the word and excludes punctuation. XmlCamelCaseInterceptor is registered for text/xml and, when the useCamelCaseStyleNavigation preference is on, sets the next or previous offset to an uppercase boundary inside a TAG, ARGUMENT, TEXT, VALUE, PI_TARGET, PI_CONTENT, or CDATA_SECTION token, and only while the run up to that boundary is still an identifier. A disabled preference, a non-text token such as a comment, or a rejected character before the hump leaves the offset unset so the default word scan runs. XmlCamelCaseInterceptorTest covers the acceptor and those forward, backward, punctuation, markup, and comment offsets.

In an XML buffer such as a Maven POM, Ctrl-Shift-Left and Ctrl-Shift-Right extend the selection across a whole element name or value. Movement does not stop at punctuation in values such as org.apache.maven or maven-compiler-plugin, or at camel-case boundaries in names such as artifactId. The XML identifier acceptor treated every character as part of a word except whitespace and the markup characters <, >, &, quotes, slash, and backslash, so dots and hyphens stayed inside the word. text/xml had no CamelCaseInterceptor, so a run of identifier characters was never split where a lowercase sequence meets an uppercase letter.

Fixes #9664

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