Feat (float): adding new attributes to proxy and quant tensor

[i-colbert]

Reason for this PR

Adding features to float quant tensor and proxy for symmetry with integer quantizers.

Changes Made in this PR

Added .bit_width() to float quant proxy and .int() to float quant tensor.

Testing Summary

Adding tests to check .int() dynamic range and _CacheIO behavior.

Risk Highlight

• This PR includes code from another work (please detail).
• This PR contains API-breaking changes.
• This PR depends on work in another PR (please provide links/details).
• This PR introduces new dependencies (please detail).
• There are coverage gaps not covered by tests.
• Documentation updates required in subsequent PR.

Checklist

• Code comments added to any hard-to-understand areas, if applicable.
• Changes generate no new warnings.
• Updated any relevant tests, if applicable.
• No conflicts with destination dev branch.
• I reviewed my own code changes.
• Initial CI/CD passing.
• 1+ reviews given, and any review issues addressed and approved.
• Post-review full CI/CD passing.