Add pagination for File Blame page

What does this MR do and why?

Contributes to #225174 (closed)

Feature flag issue: #360927

• Add BlameService to control pagination and blame range calculations
• Add Kaminari pagination for File Blame

Screenshots or screen recordings

Note: For this test I set PER_PAGE equal to 20

Page 1	Page 2

How to set up and validate locally

1. Enable feature flag Feature.enable(:blame_page_pagination)
2. Find a file with more than 1000 lines (or make the PER_PAGE limit lower)
3. Click on the Blame button on the file view page
4. You should see a pagination widget below the blame view

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.