Run All Feature Defaults Isolation

Feature flag defaults no longer leak between units in run --all

A feature block's default was recorded once per run and shared by every unit. During run --all, the first unit to be parsed set the value for a flag name, so a unit defining default = false could evaluate feature.toggle.value as true because a sibling unit was parsed first. Which unit won depended on parsing order, making the result vary between runs.

Defaults are now resolved per unit, including defaults inherited through include. Overrides passed with --feature or TG_FEATURE continue to apply to every unit in the run.

Thanks to @dhotcolorado for reporting and fixing this!