feat: support the SUM function in the datafusion planner

[ChunxuTang]

Similar to the implementation of the COUNT aggregation function, this PR adds the support the SUM function in the datafusion planner.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@d2056b6). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
rust/lance-graph/src/datafusion_planner.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #36   +/-   ##
=======================================
  Coverage        ?   80.44%           
=======================================
  Files           ?       16           
  Lines           ?     7426           
  Branches        ?        0           
=======================================
  Hits            ?     5974           
  Misses          ?     1452           
  Partials        ?        0           

Flag	Coverage Δ
rust-unittests	80.44% <80.00%> (?)

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