Drop support for Composer ~1.0 in the Vartheme BS4 theme and only support Composer ~2.0 and later versions

Problem/Motivation

Having mixed composer requirements opens the way to get older plugins and libraries
This brings a number of issues to new builds and the autoloader.
#3301451: Have drupal-scaffold locations web-root for Varbase as docroot to fix composer web-root folder in projects
#3302442: Drop support for Composer ~1.0 in Varbase profile and only support Composer ~2.0 and later versions

Proposed resolution

• Ditch the support for Composer ~1.0 and older plugins and libraries
• Support Composer ~2.0 and later versions ( ~2.1.0, ~2.2.0, ~2.3.0 )

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ✅ Developer Documentation support on feature change/addition
  
  Updating Varbase to work with Composer 2.0
• ➖ User Guide Documentation support on feature change/addition
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ✅ Release varbase-9.0.8, vartheme_bs4-9.0.16

Varbase update type

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Issue #3302435: Dropped support for Composer ~1.0 in the Vartheme BS4 theme and only support Composer ~2.0 and later versions