- hir_lower: add isScope=true to lowerBlock; fix resolveExprType for ekIndex,
ekField on monomorphized structs, and ekTry/ekUnwrap tmpVar typing
- lir_lower: add loop label stack for break/continue; pass null arg to
bux_task_spawn when spawn has no arguments
- lir_c_backend: multi-pass type inference for temps; include params in
varTypes; handle lvkTemp in lirLoad; use inferred type in lirAlloca