feature: Support for AWS Bedrock API Keys

[chetan]

Pull Request Type

• [x] ✨ feat
• [ ] 🐛 fix
• [x] ♻️ refactor
• [ ] 💄 style
• [ ] 🔨 chore
• [ ] 📝 docs

What is in this change?

Adds support for the relatively new authentication method using Bedrock API Keys

Also refactored some common bits between the bedrock provider and agent to make maintaining a little easier. Happy to revert if I overlooked some reason for the duplicate bits.

Additional Information

Developer Validations

• [x] I ran yarn lint from the root of the repo & committed changes
• [x] Relevant documentation has been updated
• [x] I have tested my code functionality
• [x] Docker build succeeds locally