convert all eval visualization paths to incrementally building expression trees, rather than using final eval bundles; ensure all evaluation paths, in various circumstances (single line viz, row viz), go through exactly the same path; deduplicate single-row-expr evaluation paths

src/raddbg/raddbg.h

@@ -5,6 +5,7 @@
 //~ rjf: Frontend/UI Pass Tasks
 //
 // [x] fix HRESULTs
+// [ ] fix escape char literals
 //
 // [ ] fix selecting hover eval, then hover eval disappearing, causing
 //     busted focus, until a new hover eval is opened