Fixes #1063

According to the discussion in related issue it would be good to provide references of overridden / super methods when searching for references of given method.

Example code:

object Example {

  class A { def fx(): Unit = () }
  class B extends A { override def fx(): Unit = () }
  class C extends B { override def fx(): Unit = () }
  class D extends C
  class E extends D { override def fx(): Unit = () }

  class X { def fx(): Unit = () }

  val a = new A()
  a.fx()

  val b = new B();
  b.fx()

  val c = new C();
  c.fx()

  val d = new D();
  d.fx()

  val e = new E();
  e.fx()
  
}

With current behaviour when we search for a references to 'b.fx()' we will get 2 results:

With a new behaviour searching references to the same function we will get same results plus references to overridden methods (from superclasses and subclasses):

Detailed changes:

• fix typos (symbolOccurence -> symbolOccurrence, ineheritance -> inheritance)
• change functions to need only position and not full Params object if operate only on position
• get rid of using TextParams API object internally in favor of PositionInFile
• add referencesSync (only for tests) to not have to deal with async behaviour in tests.
• move functionality of searching for all subclasses / superclasses from RenameProvider -> ReferenceProvider and put it into allInheritanceReferences function
• reuse this function in searching for references and renaming.
• test checking mentioned functionality: https://github.com/scalameta/metals/pull/1388/files#diff-bd990ebb68b0756f1af9b16a82841ef8R216
• reference results are sorted ONLY in tests to provide deterministic results.
• fix searching for parent class when parent class exists in not currently opened file.

Here (https://github.com/scalameta/metals/pull/1388/files#diff-2c60d9818336621db1490d63594edff5R151) I had to add declaration to expected results, because in tests server.references(...) creates underneath new ReferenceContext(true) (where true is for includeDeclaration) which indicates declaration should be added to results.

Finding references is not following inheritance tree in case of functions defined in methodsSearchedWithoutInheritance (e.g. toString, equals, hashCode, clone)