feat: #110 support group by column positions

[jychen7]

Which issue does this PR close?

Closes #110

What changes are included in this PR?

similar to extract and resolve alias, we create new functions to extract and resolve positions
(note: alias is resolve recursively, but position is resolve as a whole)

Are there any user-facing changes?

no

[codecov-commenter]

Codecov Report

Merging #519 (c86c061) into master (b84789a) will decrease coverage by 0.00%.
The diff coverage is 79.16%.

@@            Coverage Diff             @@
##           master     #519      +/-   ##
==========================================
- Coverage   76.09%   76.08%   -0.01%     
==========================================
  Files         155      157       +2     
  Lines       26575    26901     +326     
==========================================
+ Hits        20221    20468     +247     
- Misses       6354     6433      +79     

Impacted Files	Coverage Δ
datafusion-cli/src/lib.rs	0.00% <0.00%> (ø)
datafusion-cli/src/main.rs	0.00% <0.00%> (ø)
datafusion/src/sql/planner.rs	84.51% <90.90%> (+0.25%)	⬆️
datafusion/src/sql/utils.rs	67.61% <100.00%> (+0.82%)	⬆️
datafusion/src/physical_plan/windows.rs	86.22% <0.00%> (-0.91%)	⬇️
...lista/rust/core/src/serde/logical_plan/to_proto.rs	61.64% <0.00%> (-0.77%)	⬇️
...sta/rust/core/src/serde/logical_plan/from_proto.rs	35.41% <0.00%> (-0.51%)	⬇️
datafusion/src/optimizer/utils.rs	48.05% <0.00%> (-0.18%)	⬇️
...ta/rust/core/src/serde/physical_plan/from_proto.rs	38.51% <0.00%> (-0.14%)	⬇️
... and 7 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ee2b9ef...c86c061. Read the comment docs.

[alamb]

This is looking good @jychen7 -- thank you for the contribution 👍 A few more tests and it will be good to go from my perspective

[alamb]

👍

[alamb]

Looks great to me @jychen7 -- thank you so much!