[cfe/vm] Enable prefer_final lints in pkg/vm

As discussed by email, this adds the prefer_final_* lints to pkg/vm.

Adding the lints is a practical step forward, even though we do not enforce them with a presubmit check at this time.
Next steps including cleaning up lint violations and adding a presubmit check.

Change-Id: I50c421ad06114b1ae4a5da422b375fd28d7150d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118542
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/vm/analysis_options.yaml

@@ -6,3 +6,8 @@ analyzer:
   exclude:
     - testcases/**
     - tool/**
+linter:
+  rules:
+    - prefer_final_fields
+    - prefer_final_in_for_each
+    - prefer_final_locals