Only report isDefinition when FAR is triggered on a definition (#48566)

* Don't report isDefinition unless the starting node is a declaration

* Drop isDefinition everywhere it isn't specifically needed

* Fix tsserver tests

* Update shim comment

* Update baselines

* Add tests for isDefinition

* Update doc comment

* Clear isDefinition from all references if the first one lacks it

src/harness/client.ts

@@ -583,7 +583,6 @@ namespace ts.server {
                 fileName: entry.file,
                 textSpan: this.decodeSpan(entry),
                 isWriteAccess: entry.isWriteAccess,
-                isDefinition: false
             }));
         }