Rename `Module` as `JacksonModule` in 3.0 (to avoid overlap with `java.lang.Module`)

[cowtowncoder]

At the time, com.fasterxml.jackson.databind.Module was not problematic, but with Java 9 and later there is now Module in java.lang -- requiring explicit package name for Jackson's Module, everywhere.
While this is how it has to be for 2.x, let's rename base abstraction in 3.0.

[cowtowncoder]

All went well until Scala module, which apparently has type JacksonModule.scala.
Will need to file a separate issue there.