Add minimum-level support

In order to support native image generation with Quarkus, we need to be able to minimize the size of the image. In order to do this, introduce a "minimum level" property on logger nodes. This value is permanent after the creation of the node, and can be constant-folded by native image compilers, which allows the compiler to detect the fact that logging statements and blocks for levels below the minimum can be deleted from the image, which in turns reduces the reachability graph produced by these operations and thus further reduces image size.

The default minimum level would be `ALL`, which matches the existing WildFly behavioral expectation.