refactor(binder): use align_types for coalesce

[xiangjinwu]

What's changed and what's your intention?

align_types allows a list of exprs that implicitly castable to the same type.

dev=> select coalesce(1, 1.2);
 expr#0 
--------
 1
(1 row)

dev=> select coalesce(date '2020-01-01', timestamp '2020-01-01 01:02:03');
       expr#0        
---------------------
 2020-01-01 00:00:00
(1 row)

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)

#2308

[codecov]

Codecov Report

Merging #2382 (ebbc3d9) into main (27fc53b) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2382      +/-   ##
==========================================
- Coverage   71.24%   71.24%   -0.01%     
==========================================
  Files         680      680              
  Lines       86111    86097      -14     
==========================================
- Hits        61353    61339      -14     
  Misses      24758    24758              

Flag	Coverage Δ
rust	71.24% <100.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
src/frontend/src/binder/expr/function.rs	91.07% <100.00%> (-1.36%)	⬇️
src/frontend/src/expr/function_call.rs	99.29% <100.00%> (+0.03%)	⬆️

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[neverchanje]

lgtm @cykbls01 Please take a look.