Revert "Generate lambdas to access default config methods"

[rgallardo-netflix]

Reverts #664

Users are seeing errors related to this change

...
Caused by:
    java.lang.invoke.LambdaConversionException: Invalid receiver type interface com.netflix.webclient.core.config.WebClientProperties$EnabledSupported; not a subtype of implementation receiver type interface com.netflix.webclient.core.config.WebClientProperties$Codecs
    at java.lang.invoke.AbstractValidatingLambdaMetafactory.validateMetafactoryArgs(AbstractValidatingLambdaMetafactory.java:240)
    at java.lang.invoke.LambdaMetafactory.metafactory(LambdaMetafactory.java:303)
    at com.netflix.archaius.ConfigProxyFactory.asFunction(ConfigProxyFactory.java:439)