Upstreaming Intervals

- Acceded to request to import reflective calls by warnings
- Tests often need updating with `DontCare`s
- IntervalChainedSubTester works on Treadle not in verilator right now
- Bit width of range"[0,0]" is 1
- Added DontCare to valid connect argument for Interval
- Use binary point (when known) to shiftRight computation on Interval

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