Fix bug where graph-merger updates have equal forward_edge_name/reverse edge_name.

[wimax-grapl]

Which issue does this PR correspond to?

none. discovered today

What changes does this PR make to Grapl? Why?

I noticed in analyzer logging that the Updates we were getting had the same value for forward/reverse. That's wrong!

The easiest way to get the reverse edge name is to forward it from graph-mutation, which already does that lookup (and caches it).

How were these changes tested?

Added an integration test!

[codecov]

Codecov Report

Base: 41.36% // Head: 41.37% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (10b2891) compared to base (d9d2e2d).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2100      +/-   ##
==========================================
+ Coverage   41.36%   41.37%   +0.01%     
==========================================
  Files         406      406              
  Lines        9910     9910              
==========================================
+ Hits         4099     4100       +1     
+ Misses       5811     5810       -1     

Impacted Files	Coverage Δ
src/rust/graph-merger/src/service.rs	0.00% <ø> (ø)
...rust-proto/src/graplinc/grapl/api/graph/v1beta1.rs	50.81% <0.00%> (-0.33%)	⬇️
src/rust/sysmon-parser/src/util.rs	41.33% <0.00%> (+1.33%)	⬆️

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