feat: introduce Resolver as a drop in replacement for Evaluator

[Kavindu-Dodan]

This PR

To have consistent naming, I have introduced Config.Resolver as a drop-in replacement of Config.Evaluator. No breaking change as internal handling is done through a common interface.

Old

FlagdProvider flagdProvider = new FlagdProvider(
        FlagdOptions.builder()
                .resolverType(Config.Evaluator.IN_PROCESS)
                .build());

New

FlagdProvider flagdProvider = new FlagdProvider(
        FlagdOptions.builder()
                .resolverType(Config.Resolver.IN_PROCESS)
                .build());

Config.Evaluator is deprecated and will be removed in a future release.

[toddbaert]

Thanks