include symbol occurrence of meta annotations in semantic db

[swachter]

The package scala.annotation.meta contains a couple of meta annotations that when being used are not included as symbol occurrences in SemanticDB text documents.

Example (from ScalaJS):

import scala.scalajs.annotation.JSExport
import scala.annotation.meta.field
class C(@(JSExport @field) val x)

The symbol occurrence of JSExport at line 3 is recorded whereas the field annotation isn't.