refactor(proto): remove TypeName::Symbol and Char

[fuyufjh]

What's changed and what's your intention?

As title.

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)

closes #2568

[codecov]

Codecov Report

Merging #2574 (a761b07) into main (ac6ba46) will increase coverage by 0.17%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2574      +/-   ##
==========================================
+ Coverage   71.93%   72.11%   +0.17%     
==========================================
  Files         676      678       +2     
  Lines       87564    88106     +542     
==========================================
+ Hits        62991    63538     +547     
+ Misses      24573    24568       -5     

Flag	Coverage Δ
rust	72.11% <100.00%> (+0.17%)	⬆️

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

Impacted Files	Coverage Δ
src/expr/src/expr/expr_literal.rs	90.99% <ø> (+0.25%)	⬆️
src/common/src/types/mod.rs	65.50% <100.00%> (-0.07%)	⬇️
src/expr/src/expr/build_expr_from_prost.rs	69.71% <100.00%> (ø)
src/expr/src/expr/expr_unary.rs	75.72% <100.00%> (ø)
src/storage/src/object/mod.rs	13.63% <0.00%> (-1.75%)	⬇️
src/expr/src/expr/mod.rs	47.61% <0.00%> (-1.17%)	⬇️
src/storage/src/store_impl.rs	5.79% <0.00%> (-0.99%)	⬇️
src/frontend/src/handler/create_index.rs	86.71% <0.00%> (-0.49%)	⬇️
src/frontend/src/catalog/catalog_service.rs	7.52% <0.00%> (-0.34%)	⬇️
src/common/src/types/ordered_float.rs	24.70% <0.00%> (-0.20%)	⬇️
... and 34 more

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