Merge release 7.9.0 (#7742)

* Update versions for Release 7.9.0

* Fix pod lib lint for watchOS + add CI test (#7740)

* Fix pod lib lint for watchOS

* Add watchOS build test.

* Code review feedback

* Typo and formatting

* Typo and formatting

* fix typo

* Add missing test util files to tests targets

Co-authored-by: Maksym Malyhin <mmaksym@google.com>

* Resolve new SPM package install warning (#7741)

Co-authored-by: Ryan Wilson <wilsonryan@google.com>
Co-authored-by: Paul Beusterien <paulbeusterien@google.com>

FirebaseABTesting.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'FirebaseABTesting'
-  s.version          = '7.8.0'
+  s.version          = '7.9.0'
   s.summary          = 'Firebase ABTesting'
 
   s.description      = <<-DESC