fix(tracing): resolve OpenTelemetry warnings and token type error

[Malagurti]

Description

• Fix try_get_openai_tokens method indentation causing AttributeError
• Convert all token values to float type to resolve OpenTelemetry warnings
• Improve error handling in token collection methods
• Add safe type conversion for dictionary and None values
• Ensure consistent numeric values for all token fields
• Fix token inheritance between parent/child spans

Fixes: #3880 #3888

All Promptflow Contribution checklist:

• The pull request does not introduce [breaking changes].
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.
• I confirm that all new dependencies are compatible with the MIT license.
• Create an issue and link to the pull request to get dedicated review from promptflow team. Learn more: suggested workflow.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[Malagurti]

@microsoft-github-policy-service agree

[github-actions]

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