[Enhancement] Adding AWS as a provider to the models

[abhi9cr7]

Overview

PR Title: AWS support
Author: Abhi G
Date of Review: August 9th 2025

Summary

Current models.py file contains only OpenAI and Azure authentication. This pull request adds AWS auth allows users to select from wide range of models available on Bedrock.

Functionality & Implementation:

• Added langchain-aws to the requirements
• Added OpenAI as the default provider in the experimental folder to make sure current tests do not fail
• Updated models.py to use ChatBedrockConverse and BedrockEmbeddings if AWS is passed as the model provider
• Added ability to pass an existing AWS Profile from an AWS credential file, or Access Key, Secret & Tokens
• Made the above mentioned changes to both the experimental and pkg folders

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @abhi9cr7 to sign the Salesforce Inc. Contributor License Agreement.

[abhi9cr7]

@joeconstantino @stephenlprice I am not sure who from Tableau needs to review this PR. Can you please review this PR, or tag appropriate people?

[abhi9cr7]

@allisonbierschenk thanks for reviewing. Can you please merge the code changes? I don't have write permissions.