fix(ui): use new quantity field across components

[cmatzenbach]

Description

The stats-quantities branch introduces a quantity field on OperatorStatistic and rescales duration values from nanoseconds to seconds on the backend before sending them to the UI. Without corresponding FE changes, all _ns duration statistics display incorrect values - the existing inferFieldFormatter treated the value as nanoseconds, but it's now receiving seconds, causing values to be off.

This wires the quantity field through to every display site so values are formatted using the QuantitySpec from QueryBundle.quantity_specs rather than name-based heuristics.

Display sites updated:

• DAGNodeInfoPanel - the operator detail panel now formats stats via formatStatWithQuantity, receiving quantity_specs as a new prop from QueryPlan
• QueryPlanNode - the node color label uses formatStatWithQuantity
• DAGLegend - continuous color legends use formatQuantity directly when a resolved QuantitySpec is available
• PivotedStatTable - formatStatValue/formatNumericStat accept an optional QuantitySpec; the operator table computes a statQuantitySpecs map from quantity_specs and threads it through to the table cells

Related Issues

Relates to PR rapidsai#471

Testing

• Click a node in the DAG - confirm duration stats in the info panel show human-readable values (e.g. "1.23 ms", "450 µs") rather than near-zero numbers
• Color nodes by a duration stat - confirm the node label and legend min/max are formatted correctly
• Open the operator stats pivot table - confirm duration columns display correctly in both raw and aggregated modes
• Confirm byte stats (e.g. spill_bytes) still format correctly - these were already working and should be unaffected