use pekko: in urls and fix other branding issues (#184)

* use pekko: in urls and fix other branding issues

* update comments

* fix artery test

* test changes

* scalafmt

* try to fix some tests and fixing more akka refs

* more akka refs

* more changes

* more akka refs

* Update LeaseMajoritySpec.scala

* Update docs/src/main/paradox/testing.md

Co-authored-by: Johannes Rudolph <johannes.rudolph@gmail.com>

* Update docs/src/main/paradox/project/migration-guides.md

Co-authored-by: Johannes Rudolph <johannes.rudolph@gmail.com>

* Update actor/src/main/scala/org/apache/pekko/serialization/Serialization.scala

Co-authored-by: Johannes Rudolph <johannes.rudolph@gmail.com>

* Update scripts/release-train-issue-template.md

Co-authored-by: Johannes Rudolph <johannes.rudolph@gmail.com>

* revert link-validation change

* Update JacksonModule.scala

* revert key name changes to fix 2 tests

* fix one test

* more test trouble

* more test issues

* fix hashing test

* Update RouterTest.java

* update code comment

---------

Co-authored-by: Johannes Rudolph <johannes.rudolph@gmail.com>

docs/src/test/java/jdocs/testkit/TestKitDocTest.java

@@ -518,7 +518,7 @@ public class TestKitDocTest extends AbstractJavaTest {
 
         final int result =
             new EventFilter(ActorKilledException.class, system)
-                .from("akka://TestKitDocTest/user/victim")
+                .from("pekko://TestKitDocTest/user/victim")
                 .occurrences(1)
                 .intercept(
                     () -> {