Add Anthropic Token Usage Callback Handler

[shahad-mahmud]

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Feature request

Add AnthropicTokenUsageCallbackHandler and related functions to track Anthropic usage and cost. I know there is a callback handler for Bedrock Anthropic models, but no callback handler for the Anthropic APIs.

Motivation

The OpenAI callback handler makes it convenient to track OpenAI usage. Similar to Antropic would make the development experience easier.

Proposal (If applicable)

I can implement the callback handler and create a PR with the help of the contributors and maintainers.