Fix code select and organize imports for `@NamedParam` in the presence of `@NamedVariant`

[eric-milles]

Consider the following:

import groovy.transform.NamedParam
import groovy.transofrm.NamedVariant
class C {
  @NamedVariant foo(@NamedParam bar, @NamedParam baz) {
    // ...
  }
}

Code hover/select for "NamedParam" does not show groovy.transform.NamedParam. And organize imports (Ctrl+Shift+O) removes the import groovy.transform.NamedParam line.

[eric-milles]