refactor(optimizer): LogicalProject::with_mapping should return Self

[Enter-tainer]

What's changed and what's your intention?

As the title, make LogicalProject::with_mapping return Self rather than PlanRef, allowing better code reuse.

The logic for empty projection is changed as well. We should return an empty projection rather than directly return input.

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #2566 (ba66596) into main (10cce2e) will increase coverage by 0.00%.
The diff coverage is 88.88%.

@@           Coverage Diff           @@
##             main    #2566   +/-   ##
=======================================
  Coverage   72.08%   72.08%           
=======================================
  Files         677      677           
  Lines       88006    88011    +5     
=======================================
+ Hits        63439    63444    +5     
  Misses      24567    24567           

Flag	Coverage Δ
rust	72.08% <88.88%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...c/frontend/src/optimizer/plan_node/logical_topn.rs	85.24% <0.00%> (-0.71%)	⬇️
...rc/frontend/src/optimizer/plan_node/logical_agg.rs	97.65% <100.00%> (+<0.01%)	⬆️
...frontend/src/optimizer/plan_node/logical_filter.rs	97.89% <100.00%> (+0.01%)	⬆️
...tend/src/optimizer/plan_node/logical_hop_window.rs	99.36% <100.00%> (+<0.01%)	⬆️
...c/frontend/src/optimizer/plan_node/logical_join.rs	87.51% <100.00%> (+0.01%)	⬆️
...rontend/src/optimizer/plan_node/logical_project.rs	98.77% <100.00%> (ø)
...frontend/src/optimizer/plan_node/logical_source.rs	64.40% <100.00%> (ø)
src/connector/src/filesystem/file_common.rs	80.35% <0.00%> (-0.45%)	⬇️
src/common/src/types/ordered_float.rs	24.90% <0.00%> (+0.19%)	⬆️
src/meta/src/model/barrier.rs	82.14% <0.00%> (+3.57%)	⬆️

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more