llms/bedrock: Add AWS Bedrock LLMs

[sansmoraxz]

Adding bedrock LLMs.

Namely the models from following providers:-

• A21 Labs (Jurrasic Mid & Ultra)
• Amazon (Titans)
• Claude (v1-instant, v2, v2.1, v3-sonnet, v3-haiku)
• Cohere Command (Normal & Lite)
• Meta (Llama 2- 13B and 70B Chat)

PR Checklist

• Read the Contributing documentation.
• Read the Code of conduct documentation.
• Name your Pull Request title clearly, concisely, and prefixed with the name of the primarily affected package you changed according to Good commit messages (such as memory: add interfaces for X, Y or util: add whizzbang helpers).
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. Fixes #123).
• Describes the source of new concepts.
• References existing implementations as appropriate.
• Contains test coverage for new functions.
• Passes all golangci-lint checks.

[sansmoraxz]

Also IMO some CallOptions should be of pointer type, otherwise there is no way to differentiate unpassed parameters. For instance, temperature value 0 may be set explicitly or it may just be the default value (which would in turn overload LLM defaults).

[tmc]

Please comment new exported symbols.

[tmc]

Thanks so much, can you follow up and open a PR to add examples for this? Great contribution!