Move activity finish methods to ActivityRecord

Methods dedicated to finishing activities in ActivityStack mostly
operate with internal ActivityRecord state and call ActivityRecord
methods, so it makes sense to move them there.

No change in functionality, only code being moved around.

Bug: 137329632
Test: Build and flash
Change-Id: Ic3555c3279a5e918925fc4bae3a4d2fa6b35fd74
diff --git a/services/core/java/com/android/server/wm/ActivityTaskManagerService.java b/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
index c37ced5..03af388 100644
--- a/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
+++ b/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
@@ -1646,7 +1646,8 @@
                 if (getLockTaskController().activityBlockedFromFinish(r)) {
                     return false;
                 }
-                return task.getStack().finishActivityAffinityLocked(r);
+                r.finishActivityAffinity();
+                return true;
             } finally {
                 Binder.restoreCallingIdentity(origId);
             }