[Feat]: add AWS STS assume-role and SigV4 signing for Bedrock

[samadpls]

Fixes #690

• Added support for AWS credentials configuration in the schema and configuration files.
• Introduced functions to retrieve AWS credentials from the environment and sign requests using AWS Signature Version 4.
• Updated the StreamContext and FilterContext to handle AWS credentials and integrate with Bedrock services.
• Added new error handling for AWS-related operations.
• Updated Cargo.toml files to include necessary AWS dependencies and features.