http_client and http_async_client bugfix

[PranavPuranik]

Description

This would allow users to use pass proxy servers via config. It would allow them to use Embedchain behind a company's proxy setting.

Current implementation lacks creating of httpx or any HttpClient interface. It expects user a client in config, but there is no documentation on how to use it. I also believe its not possible to pass it this http_client value from the config.

This PR allows http proxies to be passed down from config instead, including async proxies (all
examples in unit tests). It creates a httpx.Client or httpx.AsyncClient as mentioned in the Langchain docs on behalf of the user.

Fixes #1452

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• Documentation update

How Has This Been Tested?

I tested this on my AzureOpenAI instance, but could not test it for Openai.

I have unit tests for both, other pr adds azure.

• Unit Test
• Test Script (please provide)

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

[stnbSim]

Hi @deshraj, any chance it will be included in the next release?