[roll] Roll fuchsia [fidl][cpp] Correctly discard unknowns in natural tables and unions

Previously natural tables did not handle unknown envelopes. Decoding
fails due to unconsumed bytes and handles. GIDL did not fail because
there's a logic to skip any test dealing with unknowns in the natural
C++ GIDL generator. Some skipping were moved to GIDL allow/denylisting
in this CL and we should represent all the skipping in GIDL
allow/denylists eventually.

PS1 is a simple fix but performance is too slow:

  CPP/Decode/Table/AllSet/63/Steps.Decode/WallTime
  slower            1.390-1.434    636.6 +/- 8.9 ns     898.8 +/- 1.6 ns
  CPP/Decode/Table/SingleSet/1_of_63/Steps.Decode/WallTime
  slower            1.577-1.616    423.8 +/- 3.4 ns     676.7 +/- 2.9 ns

After inspecting the assembly using `fx dis`, it turns out the compiler
no longer flattens the tail calls used when traversing table members. I
got a `std::apply` + fold trick working to ensure that we avoid tail
calls in the first place. The same technique could be applied to all
visitation down the road. In PS 5 we have:

  CPP/Decode/Table/AllSet/63/Steps.Decode/WallTime
  faster            0.777-0.797    637.3 +/- 1.9 ns     501.6 +/- 4.8 ns
  CPP/Decode/Table/SingleSet/1_of_63/Steps.Decode/WallTime
  faster            0.504-0.515    419.5 +/- 2.3 ns     213.8 +/- 1.2 ns

These benchmark got slower:

  CPP/Decode/Table/LastSetOthersReserved/16/Steps.Decode/WallTime
  slower            1.264-1.290    153.43 +/- 0.25 ns   196.0 +/- 1.7 ns
  CPP/Decode/Table/LastSetOthersReserved/63/Steps.Decode/WallTime
  slower            2.168-2.314    156.2 +/- 3.5 ns     349.9 +/- 3.6 ns

But there's less room to optimize because now the decoder has to perform
extra work to inspect and close all those reserved envelopes.

Original-Fixed: 111372
Original-Bug: 85383
Original-Bug: 111709
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/737167
Original-Revision: 71462b0ff734ec8ff3f9e47fc52f437e8cc336c0
GitOrigin-RevId: e5cc44ba1ecfc91050794e834821d5fb8155512d
Change-Id: I74b0c094078ddfa4a0b99f77dbb83e67765b48ad