Add self-loop-edge

[andyfengHKU]

Add support for self-loop edge e.g. (a)-[e]->(a). For read query, we rewrite it as (a)-[e]->(b) WHERE id(a) = id(b)

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (eb31b2e) 91.18% compared to head (21c8c7d) 91.18%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1815   +/-   ##
=======================================
  Coverage   91.18%   91.18%           
=======================================
  Files         777      777           
  Lines       28447    28459   +12     
=======================================
+ Hits        25939    25950   +11     
- Misses       2508     2509    +1     

Impacted Files	Coverage Δ
src/binder/bind/bind_graph_pattern.cpp	96.18% <ø> (-0.03%)	⬇️
src/include/binder/expression/rel_expression.h	100.00% <ø> (ø)
src/binder/bind/bind_reading_clause.cpp	95.91% <100.00%> (+1.32%)	⬆️
src/include/binder/expression/expression.h	91.30% <100.00%> (+0.39%)	⬆️
...rc/include/binder/expression/node_rel_expression.h	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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