Use symlinks when looking for module names for declaration emit (#24874)

* fix symlink tag, support arbitrary (ie, directory) links via @link

Introduce indirect symlink lookup to specifier deriver

Use fileset, move exec

vfs path resolution :shakes fist:

Apply files symlink relative to dirname

Use directory function

* Accept really bad baseline updates

src/testRunner/compilerRunner.ts

@@ -179,7 +179,9 @@ class CompilerTest {
             this.otherFiles,
             this.harnessSettings,
             /*options*/ tsConfigOptions,
-            /*currentDirectory*/ this.harnessSettings.currentDirectory);
+            /*currentDirectory*/ this.harnessSettings.currentDirectory,
+            testCaseContent.symlinks
+        );
 
         this.options = this.result.options;
     }