Add loader for map dataType

[acquamarin]

Format of map column in csv:
{key1=val1, key2=val2, key3=val3}

[codecov]

Codecov Report

Patch coverage: 90.74% and project coverage change: -0.24% ⚠️

Comparison is base (315d7c7) 89.69% compared to head (d67eaff) 89.46%.

❗ Current head d67eaff differs from pull request most recent head d116825. Consider uploading reports for the commit d116825 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1891      +/-   ##
==========================================
- Coverage   89.69%   89.46%   -0.24%     
==========================================
  Files         868      839      -29     
  Lines       30948    30739     -209     
==========================================
- Hits        27760    27501     -259     
- Misses       3188     3238      +50     

Files Changed	Coverage Δ
src/include/storage/copier/table_copy_utils.h	100.00% <ø> (ø)
src/include/storage/copier/var_list_column_chunk.h	100.00% <ø> (ø)
src/storage/copier/table_copy_utils.cpp	72.81% <85.48%> (+0.72%)	⬆️
src/common/types/types.cpp	90.00% <95.83%> (+0.63%)	⬆️
src/common/types/value.cpp	84.42% <100.00%> (+0.20%)	⬆️
src/include/storage/store/var_list_node_column.h	100.00% <100.00%> (ø)
src/storage/copier/column_chunk.cpp	73.70% <100.00%> (-3.45%)	⬇️
src/storage/copier/var_list_column_chunk.cpp	87.50% <100.00%> (+1.22%)	⬆️
...e/in_mem_storage_structure/in_mem_column_chunk.cpp	32.93% <100.00%> (ø)
.../storage/in_mem_storage_structure/in_mem_lists.cpp	67.43% <100.00%> (ø)
... and 2 more

... and 300 files with indirect coverage changes

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