Add conversion support to MeasureUnit

[younies]

Description

This update introduces the followings

• The ConversionInfo class to the MeasureUnit, which encapsulates conversion details such as conversion rates and offsets to the base unit.
• Additionally, a new method, convertFrom, is implemented to facilitate conversions between MeasureUnits, ensuring proper handling of mixed units and convertibility checks.
• The constructor for MeasureUnit is also updated to accommodate the new conversion information.

TODO: Please describe your changes here.

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Checklist

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[macchiati]

Looking pretty good

[macchiati]

The cache of measure units should use ConcurrentHashMaps, not synchronization.