Previously, the `Xliff2TranslationParser` only matched files that had a narrow
choice of extensions (e.g. `xlf`) and also relied upon a regular expression
match of an optional XML namespace directive.
This commit relaxes the requirement on both of these and, instead, relies
upon parsing the file into XML and identifying an element of the form
`<xliff version="2.0">` which is the minimal requirement for such files.
PR Close#35793
08071e5634