Consistent ordering for @PropertySource locations

Ensure that property source locations are processed in the same order
regardless if the 'name' attribute is set or not.

Prior to this commit multiple locations from a `@PropertySource` with
a name were added to a `CompositePropertySource` in such a way that
the first location would take precedence. This has now been reversed
for consistence with unnamed `@PropertySource`s

Issue: SPR-10820