In #8568 we optimized the grouping of locals in the binary writer to account for how types will be written given the enabled features. However, that change did not properly update the handling of scratch locals accordingly, leading to inconsistencies in the indices assigned to local types in different locations. Fix the problem by reverting the changes from #8568 and handling the mapping from IR types to written types at a lower level; specifically, create a new `TypeIndexMap` type that extends `InsertOrderedMap` but always applies `asWrittenGivenFeatures` to its keys. Use this new map type both for the `numLocalsByType` map and the `scratchLocals` map.