Filter out empty auxiliary groups

[kwridan]

Resolves: #6141

Short description 📝

• Add cached artifacts into a new group called /Cache #6057 introduced a Cache group to help distinguish cached artifacts from system libraries
• This didn't account for cases where the cache or cloud features aren't in use thus causing an additional Cache group to appear in all generated projects
• As a short term mitation we can filter out empty "auxiliary" groups at the end of the project generation steps
• This includes groups Xcode doesn't have by default including the Frameworks group which it only adds if a system library dependency is added

Notes 📝

• The Product group isn't treated as an auxiliary group as Xcode always has this group in the generated pbxproj, the UI however hides it when empty
• A longer term solution would be extend the project/target API to allow the cache mapper to add groups instead of TuistGenerator having awareness about the cache feature

How to test the changes locally 🧐

• Generate the fixture ios_app_with_tests
• Verify the Frameworks and Cache groups are no longer present
• Generate the fixture ios_app_with_sdk
• Verify the Frameworks group is still present (as there are system library dependencies)
• Verify the Cache group is no longer present

Contributor checklist ✅

• The code has been linted using run mise run lint:fix
• The change is tested via unit testing or acceptance testing, or both
• The title of the PR is formulated in a way that is usable as a changelog entry
• In case the PR introduces changes that affect users, the documentation has been updated

Reviewer checklist ✅

• The code architecture and patterns are consistent with the rest of the codebase
• Reviewer has checked that, if needed, the PR includes the label changelog:added, changelog:fixed, or changelog:changed, and the title is usable as a changelog entry