Fix issue-2343

[andyfengHKU]

Fix issue #2343

The problem is because we use LogicalType to check if a variable is a Node/RelExpression or not. This is no longer true for the case of UNWIND, e.g. MATCH (a) WITH collect(a) AS b UNWIND b AS c RETURN c, c has LogicalType NODE but is not a NodeExpression.

In this PR we introduce PATTERN expression type to differentiate the above case. With this PR, a will be treated as an expression with ExpressionType PATTERN and LogicalType NODE while c will be treated as an expression with ExpressionType VARIABLE and LogicalType NODE.

In addition, we use enum class for ExpressionType

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (3f7fb1b) 90.76% compared to head (1831aca) 90.80%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2366      +/-   ##
==========================================
+ Coverage   90.76%   90.80%   +0.03%     
==========================================
  Files        1016     1015       -1     
  Lines       35710    35730      +20     
==========================================
+ Hits        32412    32444      +32     
+ Misses       3298     3286      -12     

Files	Coverage Δ
src/binder/bind/bind_file_scan.cpp	98.38% <100.00%> (ø)
src/binder/bind/bind_projection_clause.cpp	93.57% <100.00%> (+0.18%)	⬆️
src/binder/bind/bind_updating_clause.cpp	98.46% <100.00%> (+3.04%)	⬆️
...binder/bind_expression/bind_boolean_expression.cpp	100.00% <100.00%> (ø)
...rc/binder/bind_expression/bind_case_expression.cpp	100.00% <100.00%> (ø)
...der/bind_expression/bind_comparison_expression.cpp	100.00% <100.00%> (ø)
...inder/bind_expression/bind_function_expression.cpp	98.14% <100.00%> (+0.04%)	⬆️
src/binder/expression/expression.cpp	88.88% <100.00%> (ø)
src/binder/expression/expression_util.cpp	85.18% <100.00%> (+3.36%)	⬆️
src/binder/expression_binder.cpp	95.23% <100.00%> (ø)
... and 34 more

... and 3 files with indirect coverage changes

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