Polish
Guard default conversion service creation

Update ConfigurationPropertiesBindingPostProcessor to ensure that
the defaultConversionService is only created once.

Fixes gh-1822
Optimize property sources pattern matching

Create a PropertyNamePatternsMatcher strategy interface that
PropertySourcesPropertyValues can use to determine when a property
can be used.

PropertiesConfigurationFactory uses DefaultPropertyNamePatternsMatcher
which is heavily optimized for frequent calls.

Fixes gh-1823