Cannot load XSLT custom function from a class in the current application

A followup of https://github.com/apache/camel-quarkus/pull/3526#issuecomment-1032535928

There is a known limitation in #3526 that custom function classes have to be defined in a separate jar for the transformer to be able to load them. I think this is caused by the fact that TransformerFactory class is resolved using a wrong class loader around here in Camel https://github.com/apache/camel/blob/camel-3.15.0/components/camel-xslt/src/main/java/org/apache/camel/component/xslt/XsltEndpoint.java#L372
Perhaps changing that (or better making configurable) to current thread class loader could solve the problem.

Here are some changes needed to test the potential fix: https://github.com/ppalaga/camel-quarkus/commits/i3534