Foundation PR for Tax Calc: Conditional BYS page + journey skeleton added

[ayubAz]

Add skeleton framework ahead of Tax calculation flow:

• The first three flows are almost identical apart from conditional logic in the view
• The fourth flow has some differences and depends on the isLeaseholdSelfAssessed flag
• Created:

1. Required Pages
2. Required routing in navigator, currently all redirect to Index (to be updated incrementally as we work on the journey)
3. Dummy navigator tests to be updated

[platops-pr-bot]

• uk.gov.hmrc:bootstrap-frontend-play-30 can be updated to 10.7.0 in project/AppDependencies.scala.
• uk.gov.hmrc:play-frontend-hmrc-play-30 can be updated to 12.32.0 in project/AppDependencies.scala.
• uk.gov.hmrc:bootstrap-test-play-30 can be updated to 10.7.0 in project/AppDependencies.scala.