bedrockclient: add support for new Amazon Nova models

[oryanmoshe]

PR Checklist

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• 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).
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This PR adds support for the new Amazon Nova models
The implementation is very similar to the anthropic provider (since they share some common structures and constraints)

[oryanmoshe]

Hi @tmc, any chance to get a review for these changes? (:
Thanks!