Integrate GVN info

[bvisness]

We have all this lovely GVN info that gets tracked when IONFLAGS=gvn is active:

[GVN] Running GVN on graph (with 3 blocks)
[GVN]   Visiting dominator tree (with 3 blocks) rooted at block0 (normal entry block)
[GVN]     Visiting block0
[GVN]       Discarding dead WasmNullConstant1
[GVN]       Recording WasmNullConstant2
[GVN]       Recording WasmRefAsNonNull3
[GVN]       Discarding dead WasmLoadField4
[GVN]       Replacing WasmNullConstant5 with WasmNullConstant2
[GVN]       Discarding dead WasmNullConstant5
[GVN]       Replacing WasmRefAsNonNull6 with WasmRefAsNonNull3
[GVN]       Discarding dead WasmRefAsNonNull6
[GVN]       Recording WasmLoadField7
[GVN]       Recording WasmRefTestAbstract8
[GVN]     Visiting block1
[GVN]     Visiting block2

Could we not automatically capture this same info when IONFLAGS=logs, and add that to the JSON somehow? It would be amazing to be able to pick through exactly what GVN did in context.