Remove virtual executor util and use common config in common modules.

[tomas-langer]

Resolves #4869

Requires --enable-preview to be added to a few test/compiler configs. Moved most commonly used shortcut methods to common config (asInt() etc), as we do not want a dependency on full config from common modules, and this simplifies the code (and leaves it untouched). Added method map(Function<common.config.Config, T> mapper) to common config, as it cannot be compatible with as(Function<Config, T> mapper) in config. This makes it much easier to migrate. We can eventually deprecate the as(mapper) method if we decide to.