fix: More edges in InlineDFG

[acl-cqc]

A corner case when inlining a DFG that's disconnected (no path from Input to Output, e.g. that just loads a constant) could lead to the chain/web of order edges going through the DFG being cut where the DFG was.

Fix: if there is no order path from Input to Output, then explicitly connect order-predecessors of the DFG to order-successors (we might use other criteria for the "if", but this seems a reasonable one).

[codecov]

Codecov Report

❌ Patch coverage is 95.31250% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.22%. Comparing base (abf286a) to head (7b34136).

Files with missing lines	Patch %	Lines
hugr-core/src/hugr/patch/inline_dfg.rs	95.31%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3072      +/-   ##
==========================================
+ Coverage   81.20%   81.22%   +0.01%     
==========================================
  Files         242      242              
  Lines       45622    45686      +64     
  Branches    39378    39442      +64     
==========================================
+ Hits        37048    37109      +61     
- Misses       6586     6589       +3     
  Partials     1988     1988              

Flag	Coverage Δ
python	88.88% <ø> (ø)
rust	80.01% <95.31%> (+0.02%)	⬆️

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