feat: set user being able to set chunk size and overlap for indices

[cin-cris]

Description

• chunk_size and chunk_overlap params now can be modify in the index config UI.
• About the issue about compose a new image for each time changing the flowsettings.py file, I could not find any solution to solve this. Maybe it is impossible to not build a new image.
• Fixes [REQUEST] - <title> Each user being able to set chunk size and overlap for indices. #308 (issue)

Type of change

• New features (non-breaking change).
• Bug fix (non-breaking change).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).

Checklist

• I have performed a self-review of my code.
• I have added thorough tests if it is a core feature.
• There is a reference to the original bug report and related work.
• I have commented on my code, particularly in hard-to-understand areas.
• The feature is well documented.