1.20 stable: Update engine hash to 1.20.0 (#62835)

* Update engine hash to 1.20.0

* pin customer_testing

Co-authored-by: Christopher Fujino <christopherfujino@gmail.com>
diff --git a/.cirrus.yml b/.cirrus.yml
index d9f5eea..d93dbea 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -294,6 +294,7 @@
       script:
         - rm -rf bin/cache/pkg/tests
         - git clone https://github.com/flutter/tests.git bin/cache/pkg/tests
+        - (cd bin/cache/pkg/tests; git checkout b431c1bdda8180d1537cbfdeba4b6c0ca48f1599)
         - dart --enable-asserts dev/customer_testing/run_tests.dart --skip-on-fetch-failure --skip-template bin/cache/pkg/tests/registry/*.test
 
     # firebase_test_lab_tests are linux-only
@@ -519,6 +520,9 @@
       script:
         - CMD /S /C "IF EXIST "bin\cache\pkg\tests\" RMDIR /S /Q bin\cache\pkg\tests"
         - git clone https://github.com/flutter/tests.git bin\cache\pkg\tests
+        - cd bin\cache\pkg\tests
+        - git checkout b431c1bdda8180d1537cbfdeba4b6c0ca48f1599
+        - cd ..\..\..\..
         - dart --enable-asserts dev\customer_testing\run_tests.dart --skip-on-fetch-failure --skip-template bin/cache/pkg/tests/registry/*.test
 
 # MACOS SHARDS
@@ -636,6 +640,7 @@
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
         - rm -rf bin/cache/pkg/tests
         - git clone https://github.com/flutter/tests.git bin/cache/pkg/tests
+        - (cd bin/cache/pkg/tests; git checkout b431c1bdda8180d1537cbfdeba4b6c0ca48f1599)
         - dart --enable-asserts dev/customer_testing/run_tests.dart --skip-on-fetch-failure --skip-template bin/cache/pkg/tests/registry/*.test
 
     - name: deploy_gallery-macos # linux- and macos- only
diff --git a/bin/internal/engine.version b/bin/internal/engine.version
index 6d1217f..be8d91d 100644
--- a/bin/internal/engine.version
+++ b/bin/internal/engine.version
@@ -1 +1 @@
-d6ee1499c27a156a797d9f1539ffb7892855c1d0
+c68d8a0cb71e5ea53495c3c7c77e1c41c8a18126