feat: add RemoteResponseSchema.{inserted_at,updated_at} fields

[alvarobartt]

Description

This PR adds both inserted_at and updated_at fields to RemoteResponseSchema to use those values that were previously discarded when pulling the responses from the API, which is useful for further analysis as requested by @davidberenstein1957.

Closes #3820

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested

• Add unit tests for both inserted_at and updated_at fields in RemoteResponseSchema

Checklist

• I added relevant documentation
• follows the style guidelines of this project
• I did a self-review of my code
• I made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I filled out the contributor form (see text above)
• I have added relevant notes to the CHANGELOG.md file (See https://keepachangelog.com/)

[github-actions]

The URL of the deployed environment for this PR is https://argilla-quickstart-pr-3822-ki24f765kq-no.a.run.app