docs: add docs for data model and encoding

[fuyufjh]

What's changed and what's your intention?

This describes briefly data types, semi-structure, arrays, chunks, and cell-based encoding.

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Checklist

N/A

Refer to a related PR or issue link (optional)

part of #1384

[codecov]

Codecov Report

Merging #1535 (8822d93) into main (b00df18) will decrease coverage by 0.28%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #1535      +/-   ##
============================================
- Coverage     70.44%   70.16%   -0.29%     
  Complexity     2766     2766              
============================================
  Files          1031     1031              
  Lines         90471    90690     +219     
  Branches       1790     1790              
============================================
- Hits          63735    63632     -103     
- Misses        25845    26167     +322     
  Partials        891      891              

Flag	Coverage Δ
java	61.01% <ø> (ø)
rust	72.10% <ø> (-0.35%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
rust/utils/pgwire/src/pg_protocol.rs	0.00% <0.00%> (-83.81%)	⬇️
rust/utils/pgwire/src/pg_message.rs	0.00% <0.00%> (-83.53%)	⬇️
rust/utils/pgwire/src/pg_server.rs	0.00% <0.00%> (-82.03%)	⬇️
rust/utils/pgwire/src/pg_response.rs	40.00% <0.00%> (-47.50%)	⬇️
rust/utils/pgwire/src/pg_field_descriptor.rs	46.66% <0.00%> (-30.00%)	⬇️
rust/utils/pgwire/src/types.rs	56.25% <0.00%> (-18.75%)	⬇️
rust/frontend/src/expr/subquery.rs	48.27% <0.00%> (-3.58%)	⬇️
rust/storage/src/table/cell_based_table.rs	77.55% <0.00%> (-2.99%)	⬇️
rust/frontend/src/binder/expr/mod.rs	79.11% <0.00%> (-1.41%)	⬇️
rust/stream/src/executor/dispatch.rs	77.67% <0.00%> (-0.77%)	⬇️
... and 961 more

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