Add top_p, top_k parameters, add defaults to all fields

[collindutter]

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Describe your changes

• Added type hints to Bedrock clients.
• Reorganized Driver fields to place dependent fields (clients/tokenizers) after primitive fields.
• Added top_p field to all Prompt Drivers.
• Added BasePromptDriver.additional_params to set additional request parameters such as top k.
• Added defaults to all fields. This solves an issue where users would provide a client but still be required to pass in fields like api_key.
• Removed redundant model fields as it is provided by the base class.

Issue ticket number and link

Closes #236 Closes #293