Add agat sp merge annotations

[Leila011]

Description

• add agat_sp_merge_annotations
• handle multiple inputs

Issue ticket number

Closes #xxxx

Checklist before requesting a review

• [x] I have performed a self-review of my code

• [x] Conforms to the Contributing guidelines

• [x] Proposed changes are described in the CHANGELOG.md

• [x] I have tested my code with viash ns test --parallel -q <name or namespace>

• Check the correct box. Does this PR contain:

  • [ ] Breaking changes
  • [x] New functionality
  • [ ] Major changes
  • [ ] Minor changes
  • [ ] Documentation
  • [ ] Bug fixes