Preserve source identities

[Y-Nak]

depends on #554
Preserve stable identities for qualified names, types, and specializations through lowering and Hull emission.
Fixes collisions where same-spelled declarations from different origins could be conflated or captured.

[mbenke]

Well done. Fix the merge conflicts and it's good to go.

[mbenke]

One thing I am not crazy about is that generated names are totally opaque (and long!) which makes reading the generated code (e.g. for debugging) very hard:

function usr$totalSupply () -> _result {
        let _v642
        _v642 := usr$$$S1069$$$N354$36_36_83_51_48_36_36_36_81_81_49_50_36_78_51_36_56_50_95_56_54_95_54_53_95_51
_36_57_55_95_57_57_95_57_57_95_49_36_51_49_50_36_84_54_54_36_78_49_55_36_55_55_95_49_48_49_95_49_48_57_95_57_56_9
5_49_48_49_95_49_49_52_95_54_53_95_57_57_95_57_57_95_49_48_49_95_49_49_53_95_49_49_53_95_56_48_95_49_49_52_95_49_
49_49_95_49_50_48_95_49_50_49_95_52_36_56_54_36_84_53_57_36_78_49_53_36_54_55_95_49_49_49_95_49_49_48_95_49_49_54
_95_49_49_52_95_57_55_95_57_57_95_49_49_54_95_56_51_95_49_49_54_95_49_49_49_95_49_49_52_95_57_55_95_49_48_51_95_4
9_48_49_95_49_36_49_56_36_86_49_52_36_78_51_36_57_57_95_49_50_48_95_49_49_54_95_53_56_36_86_53_52_36_78_49_51_36_
49_48_50_95_49_48_53_95_49_48_49_95_49_48_56_95_49_48_48_95_56_51_95_49_48_49_95_49_48_56_95_49_48_49_95_57_57_95
_49_49_54_95_49_49_49_95_49_49_52_95_51_55_36_86_51_51_36_78_56_36_49_48_56_95_49_49_49_95_57_55_95_49_48_48_95_5
6_52_95_49_50_49_95_49_49_50_95_49_48_49_95_52_55_36_86_52_51_36_78_49_48_36_49_49_49_95_49_48_50_95_49_48_50_95_
49_49_53_95_49_48_49_95_49_49_54_95_56_52_95_49_50_49_95_49_49_50_95_49_48_49_95_4$51$T45$N12$77_105_110_105_69_8
2_67_50_48_67_120_116_0$100$T94$N25$77_105_110_105_69_82_67_50_48_95_116_111_116_97_108_83_117_112_112_108_121_95
_115_101_108_0$34$T28$N7$117_105_110_116_50_53_54_0$272$T18$N4$112_97_105_114_2$33$T27$N6$115_116_114_105_110_103
_0$208$T18$N4$112_97_105_114_2$33$T27$N6$115_116_114_105_110_103_0$144$T18$N4$112_97_105_114_2$36$T30$N7$97_100_1
00_114_101_115_115_0$78$T18$N4$112_97_105_114_2$34$T28$N7$117_105_110_116_50_53_54_0$14$T9$N2$40_41_0$()
        _result := _v642
        leave
      }