Update Joomla Version and dependencies for 5.0 (joomla#38209)

* Update Joomla Version and dependencies for 5.0

* Unify installation/index.php with other index.ph files

* Update composer dependencies

* Disable drone composer platform checks

* Remove tests for old php versions

* Remove mysql8 tests in drone

* Update joomla cypress package

* Reset to dev 5.0.0-dev

* Sign drone and change appveyor

.appveyor.yml

@@ -8,7 +8,7 @@ clone_folder: C:\projects\joomla-cms
 environment:
   PHPBuild: "x64"
   matrix:
-  - php_ver_target: 8.0
+  - php_ver_target: 8.1
 
 
 init:
@@ -44,7 +44,8 @@ install:
     - choco install composer
     - cd C:\projects\joomla-cms
     - refreshenv
-    - composer install --no-progress --profile --ignore-platform-req=ext-sodium
+    - echo "TODO Ignore platform reqs till all composer dependencies are compatible with php 8.1"
+    - composer install --no-progress --profile --ignore-platform-req=ext-sodium --ignore-platform-reqs
 before_test:
 #  Database setup for MySQL via PowerShell tools
   - >