bugfix: Include synthetic apply in semanticdb (#23629)

Fixes scalameta/metals#7666

Some weird entries around string interpolation, but they actually make
sense.
[Cherry-picked 74b9e85]

Author: tgodzik

compiler/src/dotty/tools/dotc/semanticdb/SyntheticsExtractor.scala

@@ -77,7 +77,9 @@ class SyntheticsExtractor:
             )
           ).toOpt
 
-        case tree: Apply if tree.fun.symbol.is(Implicit) =>
+        case tree: Apply
+            if tree.fun.symbol.is(Implicit) ||
+              (tree.fun.symbol.name == nme.apply && tree.fun.span.isSynthetic) =>
           val pos = range(tree.span, tree.source)
           s.Synthetic(
             pos,