[cypress] System Tests fixes #43620, fixes #43622 (#43656)

- fixes issue #43620 - if no 'rm' command is available on Windows
- fixes issue #43622 - if cmsPath is set
- custom task 'deleteFolder' can also delete a file and ignores
  if the file does not exist -> exactly what we need
- once PR is merged i will create the next PR to rename 'deleteFolder' as 'deleteRelativePath'
  and also 'writeFile' as 'writeRelativeFile' to better represent the functions

tests/System/integration/install/Installation.cy.js

@@ -1,7 +1,5 @@
 describe('Install Joomla', () => {
   it('Install Joomla', () => {
-    cy.exec('rm configuration.php', { failOnNonZeroExit: false });
-
     const config = {
       sitename: Cypress.env('sitename'),
       name: Cypress.env('name'),
@@ -16,6 +14,8 @@ describe('Install Joomla', () => {
       db_prefix: Cypress.env('db_prefix'),
     };
 
+    // If exists, delete PHP configuration file to force a new installation
+    cy.task('deleteFolder', 'configuration.php');
     cy.installJoomla(config);
 
     cy.doAdministratorLogin(config.username, config.password, false);