+1 Simplify DotVarExp::interpret

Lazy value CTFE for the block-initialized instance field.
+2 Simplify PtrExp::interpret

All CTFE pointers now always use AddrExp, so we can rely on the representation.
+3 Simplify use of resolveSlice

Elide caller-side check for the code readability.
+4 A little simplify in SliceExp::interpret
+5 Simplify IndexExp::interpret
+6 Small cleanup in CommaExp and ArrayLengthExp
+7 Simplify interpretAssignToSlice
+7a
+8
+8a Add resolveIndexing and simplify interpretAssignToIndex