Add Validation for simple expression

[apupier]

currently only validating Camel URI.

it should be possible using
XmlRouteParser.parseXmlRouteSimpleExpressions(is, baseDir, fqn, fileSimpleExpressions);
org.apache.camel.maven.ValidateMojo.validateSimple(CamelCatalog, List)

[apupier]

might be more complicated than planned because it requires to provide the Classloader org.apache.camel.catalog.CamelCatalog to provide an accurate validation