Add batch_size in config for VectorDB

[Dev-Khant]

Description

Support to add batch_size in vectordb config.

Fixes https://embedchain.slack.com/archives/C05RG7CJKC6/p1719407963572489

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• Documentation update

How Has This Been Tested?

• Unit Test

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have 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
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed