Added http clients in config

[AbdurNawaz]

Description

embedchain's OpenAI LLM class does not allow the user to provide a custom http client. This can be done through the langchain's ChatOpenAI class which embedchain uses but does not expose the relevant arguments to change the http client. This PR exposes thehttp_client parameter into the config thereby allowing the user to change it.

Fixes #1357

Type of change

New feature (non-breaking change which adds functionality)

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

[AbdurNawaz]

@taranjeet @deshraj Can you please take a look