Summit: Add stable tiered task topo-sort for identical inputs

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This is currently works very nicely in autobuild, and means that for the same recipe tree state, you get the same task numbering and build order for consecutive clean resolves.

Potential source for how to do it:

https://github.com/GZGavinZhao/autobuild/blob/main/utils/graph.go#L77

This is a regression compared to DLang summit.