Add keyset pagination to Instance level audit events api

What does this MR do and why?

relates to: #367528 (closed)

The Audit Events interfaces do not currently have keyset pagination for the Instance level audit events API. This causes issues with large payloads

This changes implements keyset pagination, mirroring the addition of keyset pagination added to group audit events in this MR

Screenshots or screen recordings

example request 1	example request 2

How to set up and validate locally

• I set things up locally as such:

  user = User.find(1)
  group = Group.find(31)
  project = Project.find(7)
  2.times { FactoryBot.create(:project_audit_event, target_project: project, user: user) }
  2.times { FactoryBot.create(:group_audit_event, target_group: group, user: user) }

• you will need a personal access token to use in the API requests.

• Make an API query such as this (as an instance administrator)

  curl -v \
       --header "PRIVATE-TOKEN: $TOKEN" \
       -H "Content-Type: application/json" \
       -H "Accept: application/json, text/plain, */*" \
       --url "localhost:3000/api/v4/audit_events?per_page=2&pagination=keyset&order_by=id" | json_pp

• In the response headers, check the Link header which should be in this format:

  < Link: <http://127.0.0.1:3000/api/v4/projects/7/audit_events?cursor=eyJpZCI6IjYyMjAiLCJfa2QiOiJuIn0%3D&id=7&order_by=id&page=1&pagination=keyset&per_page=2>; rel="next"

• Make the same request again, using the URL provided in the LINK header

  curl -v \
       --header "PRIVATE-TOKEN: $TOKEN" \
       -H "Content-Type: application/json" \
       -H "Accept: application/json, text/plain, */*" \
       --url "http://127.0.0.1:3000/api/v4/audit_events?cursor=eyJpZCI6IjYyMjQiLCJfa2QiOiJuIn0%3D&order_by=id&page=1&pagination=keyset&per_page=2" | json_pp

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.