Add PPR sequence generation

[yliu2-sc]

Scope of work done

• Generate GT input sequence from PPR sampling
• Allow anchor based attributes to be used as either GT input or attention bias
• Add sinusoidal PE given that PPR seq is ordered by PPR weight
• PPR sampler fixed to put anchor first

Where is the documentation for this feature?: N/A

Did you add automated tests or write a test plan?

Updated Changelog.md? NO

Ready for code review?: NO