feat: alter table statement

[PangXing]

What this PR does:

Which issue(s) this PR fixes:

Fixes #165

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-commenter]

Codecov Report

Merging #184 (6e6e023) into master (df363ef) will increase coverage by 0.48%.
The diff coverage is 49.85%.

❗ Current head 6e6e023 differs from pull request most recent head 7ae076c. Consider uploading reports for the commit 7ae076c to get more accurate results

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
+ Coverage   33.31%   33.79%   +0.48%     
==========================================
  Files          78       79       +1     
  Lines       12363    12716     +353     
==========================================
+ Hits         4119     4298     +179     
- Misses       7764     7913     +149     
- Partials      480      505      +25     

Impacted Files	Coverage Δ
pkg/executor/redirect.go	9.64% <0.00%> (ø)
pkg/runtime/ast/proto.go	57.14% <ø> (ø)
pkg/runtime/ast/model.go	37.45% <31.00%> (-4.28%)	⬇️
pkg/runtime/ast/alter_table.go	34.88% <34.88%> (ø)
pkg/runtime/ast/ast.go	78.63% <65.97%> (-1.97%)	⬇️
pkg/runtime/optimize/optimizer.go	32.35% <91.30%> (+3.52%)	⬆️

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