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feat: Added optional args to `logger.log` to format string only when log level applies (#706)

## Summary
Message formatting is performance heavy. The logger takes formatted message as a parameter, which means message formatting is being done for all types of logs even in cases when the log level does not apply. This PR adds arguments array to the `log` function to carry token values. Logger already has the functionality to `sprintf` based on extra args if the log level applies. This will increase performance in cases where log level is restricted to more conservative ones such as `ERROR`.

## Test plan
- All Unit tests pass
- Manually tested thoroughly with optimizely-sdk package. A follow up PR for the main package will be created after this is merged and released.

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