Premai SDK integration

[Anindyadeep]

Description

This PR adds a integration of premai python sdk to embedchain llms and embedder.

Fixes #1366
Fixes #1368

Type of change

• New feature: Added premai python sdk
• Documentation update to add premai python sdk
• Schema validation support for custom llms and embedding models

How Has This Been Tested?

I have added tests and those are passing. You can also checkout this documentation part to reproduce it.

Please delete options that are not relevant.

• Unit Test
• Test Script ( here )

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

[Anindyadeep]

Hi @deshraj, it would be great, if we can start the review process for this, so that I can re-iterate.

Thanks and appreciate it.

ps: the code was very readible, devex experience was awesome with embedchain :)