feat: Added base_loader abstraction and updated base_io

[JoyceXu02]

Description

Added base_loader abstraction and updated base_io inherits from BaseLoader abstract class.

Checklist

Go over all the following points, and put an x in all the boxes that apply.

• I have read the CONTRIBUTION guide (required)
• I have linked this PR to an issue using the Development section on the right sidebar or by adding Fixes #issue-number in the PR description (required)
• I have checked if any dependencies need to be added or updated in pyproject.toml and poetry.lock
• I have updated the tests accordingly (required for a bug fix or a new feature)
• I have updated the documentation if needed:
• I have added examples if this is a new feature

This pr serves as a draft for fixing #1589. Still in the progress.

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