Support keyword SERIAL

[spongedu]

What problem does this PR solve?

for #467 , support keyword SERIAL.

What is changed and how it works?

1. Support SERIAL as a Numeric Type in ColumnDef
2. Support SERIAL DEFAULT VALUE as an ColumnOption
3. Add related tests

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Code changes

N / A

Side effects

N / A

[spongedu]

it's interesting that the Verify parser.go is up-to-date stage in tests is not consistent with the fmt stage. The tests will fail anyway...

[spongedu]

I think we should add a fmt command in Verify parser.go is up-to-date stage in the ci test base

[tangenta]

LGTM

[spongedu]

@leoppro PTAL :)

[codecov]

Codecov Report

Merging #481 into master will decrease coverage by 0.07%.
The diff coverage is 90.47%.

@@            Coverage Diff             @@
##           master     #481      +/-   ##
==========================================
- Coverage   71.59%   71.51%   -0.08%     
==========================================
  Files          32       32              
  Lines        7723     7689      -34     
==========================================
- Hits         5529     5499      -30     
+ Misses       1670     1668       -2     
+ Partials      524      522       -2

Impacted Files	Coverage Δ
parser.go	70.58% <ø> (ø)	⬆️
misc.go	96.42% <ø> (ø)	⬆️
ast/ddl.go	80% <90.47%> (-0.18%)	⬇️
ast/misc.go	74.05% <0%> (ø)	⬆️

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[zier-one]

LGTM please resolve conflicts
@spongedu