AWS Bedrock support

[heyjustinai]

What feature would you like?

Add AWS Bedrock as a supported inference provider with documentation and example configuration.

What's your use case?

1. Add AWS Bedrock section to docs/inference_providers.md with example YAML configuration
2. Provide setup instructions for AWS credentials (IAM roles, environment variables)
3. Add example config showing Bedrock model naming format (e.g., bedrock/meta.llama3-8b-instruct-v1:0)

Additional context

No response

[lab596]

LiteLLMModelAdapter needs to be adapted to allow for AWS - Access Key ID, Secret Access Key, and Region.

Bedrock prefix has to be added to LiteLLM - view here: https://docs.litellm.ai/docs/providers/bedrock

Update .env.example to show AWS credentials