refactor(eowc): change emit-on-window-close syntax

[stdrc]

I hereby agree to the terms of the RisingWave Labs, Inc. Contributor License Agreement.

What's changed and what's your intention?

From:

create materialized view mv emit on window close as
select
	sum(a)
from t group by a;

To:

create materialized view mv as
select
	sum(a)
from t group by a
emit on window close;

create sink sk as
select
	sum(a)
from t group by a
emit on window close
with (...);

Checklist

• [ ] I have written necessary rustdoc comments
• [ ] I have added necessary unit tests and integration tests
• [ ] I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• [ ] My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• [ ] My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR contains user-facing changes.

Click here for Documentation

Types of user-facing changes

Please keep the types that apply to your changes, and remove the others.

• SQL commands, functions, and operators

Release note

• Change syntax for Emit-On-Window-Close streaming mode

[fuyufjh]

LGTM

[codecov]

Codecov Report

Merging #11363 (d718394) into main (def4462) will increase coverage by 0.00%.
Report is 3 commits behind head on main.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main   #11363   +/-   ##
=======================================
  Coverage   70.46%   70.46%           
=======================================
  Files        1367     1367           
  Lines      225988   225992    +4     
=======================================
+ Hits       159237   159242    +5     
+ Misses      66751    66750    -1     

Flag	Coverage Δ
rust	70.46% <100.00%> (+<0.01%)	⬆️

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

Files Changed	Coverage Δ
src/sqlparser/src/keywords.rs	100.00% <ø> (ø)
src/sqlparser/src/ast/mod.rs	84.81% <100.00%> (+0.01%)	⬆️
src/sqlparser/src/ast/statement.rs	43.12% <100.00%> (+0.18%)	⬆️
src/sqlparser/src/parser.rs	86.35% <100.00%> (ø)

... and 3 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more