WIP: add a check after load to verify graph structure

[trws]

problem: We don't detect graphs with invalid upward edges in the containment tree

solution: Add a search after load for any non-tree edges of type containment, and blow up hard if we find any.

Some tests still do not pass.

@milroy, this is the WIP stuff we were discussing earlier. The RV1 test that's blowing up is t3027-resource-RV.t, but it looks like it might be an out of range error, and there are some JGFs in use in the file so it's possible it isn't an actual rv1 problem. 🤞

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 6 lines in your changes missing coverage. Please review.

Project coverage is 75.6%. Comparing base (8e47fa5) to head (4d080b0).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
resource/store/resource_graph_store.cpp	57.1%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1342     +/-   ##
========================================
- Coverage    75.7%   75.6%   -0.1%     
========================================
  Files         112     112             
  Lines       16410   16422     +12     
========================================
- Hits        12426   12425      -1     
- Misses       3984    3997     +13     

Files with missing lines	Coverage Δ
resource/traversers/dfu_impl_update.cpp	75.4% <ø> (-0.4%)	⬇️
resource/store/resource_graph_store.cpp	77.2% <57.1%> (-9.4%)	⬇️

... and 3 files with indirect coverage changes

[milroy]

The RV1 test that's blowing up is t3027-resource-RV.t, but it looks like it might be an out of range error

Test 20 (t3027-resource-RV.t) is failing because the command to generate the JSON results in an error:

$ flux R encode -r 0-1 -c 0-1 -H fluke[1-0] | jq " .execution.R_lite[0].rank |= \"0^2\" " > out20.json
flux-R: invalid hostlist 'fluke[1-0]'

and thus out20.json is empty. I'll bet the out of range error is related to running the BFS check on an empty graph. As a side note, I'm not sure if this test is working as designed.