Support defining multiple FROM TO in CREATE REL TABLE GROUP

[andyfengHKU]

This PR partially solves issue #1888 by adding a CREATE REL TABLE GROUP DDL statement to allowing creating a rel table group as a union of multiple rel tables. A subsequent PR will be submitted to allow querying a rel table group.

Together in this PR, we remove the distinction between CREATE NODE/REL/RDF table at parser, binder and planner level.

[codecov]

Codecov Report

Patch coverage: 96.52% and no project coverage change.

Comparison is base (d03d306) 89.87% compared to head (8fd6d3f) 89.88%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2009   +/-   ##
=======================================
  Coverage   89.87%   89.88%           
=======================================
  Files         884      890    +6     
  Lines       32814    32909   +95     
=======================================
+ Hits        29493    29581   +88     
- Misses       3321     3328    +7     

Files Changed	Coverage Δ
src/include/binder/binder.h	100.00% <ø> (ø)
src/include/catalog/catalog.h	100.00% <ø> (ø)
src/include/catalog/catalog_content.h	100.00% <ø> (ø)
src/include/parser/transformer.h	100.00% <ø> (ø)
...rc/include/planner/logical_plan/logical_operator.h	90.00% <ø> (ø)
src/include/processor/plan_mapper.h	100.00% <ø> (ø)
src/include/storage/wal/wal.h	100.00% <ø> (ø)
src/include/storage/wal/wal_record.h	33.76% <0.00%> (-0.91%)	⬇️
src/processor/operator/ddl/drop_table.cpp	100.00% <ø> (ø)
...processor/operator/persistent/copy_rel_columns.cpp	100.00% <ø> (ø)
... and 30 more

... and 2 files with indirect coverage changes

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