Support row based Array & fix varchar array type

[congqixia]

See also #609
/kind bug

[codecov]

Codecov Report

Merging #621 (763dfac) into master (40a4e1e) will decrease coverage by 0.56%.
The diff coverage is 2.56%.

@@            Coverage Diff             @@
##           master     #621      +/-   ##
==========================================
- Coverage   75.15%   74.60%   -0.56%     
==========================================
  Files          41       42       +1     
  Lines        4033     4063      +30     
==========================================
  Hits         3031     3031              
- Misses        890      920      +30     
  Partials      112      112              

Files	Coverage Δ
entity/columns_array_gen.go	0.00% <ø> (ø)
entity/schema.go	91.25% <100.00%> (ø)
entity/columns.go	50.38% <0.00%> (-1.20%)	⬇️
entity/rows.go	77.11% <0.00%> (-7.12%)	⬇️
entity/columns_array.go	0.00% <0.00%> (ø)

[yah01]

/lgtm

[sre-ci-robot]

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