Move UNITS registry out of tmt.hardware

[HarshRajSinghania]

Summary

Move the shared Pint UnitRegistry (UNITS) from tmt.hardware.constraints to a dedicated tmt.utils.units module so non-hardware code can convert quantities without importing tmt.hardware.

Motivation

Fixes #5171. The registry started in hardware constraints because it was only used for memory/disk sizes. It is now also used for log size limits, directory sizes, and similar values that are not hardware requirements.

Implementation

• Add tmt/utils/units.py with UNITS (and the Size type alias under TYPE_CHECKING).
• Import UNITS from there in tmt.hardware.constraints.
• Keep tmt.hardware.UNITS as a re-export so existing hardware/provision call sites keep working.
• Point non-hardware call sites at tmt.utils.units:
  • tmt.utils.normalize_data_amount
  • tmt.base.core
  • tmt.steps.report.reportportal
  • tests/unit/test_data_size_validation.py

Provision plugins (testcloud, bootc) still use tmt.hardware.UNITS; that remains valid because they already depend on hardware helpers.

Testing

Could not run the full tmt suite in this environment (project extras such as fmf are not installed here). Changes are import-path only; tmt.hardware.UNITS is the same registry object.

Suggested checks:

pytest tests/unit/test_data_size_validation.py tests/unit/test_hardware.py