Fix the error in parsing the Doris create materialized view

[jay841224]

Fixes #31499

Changes proposed in this pull request:
This pull request modify the parsing of the following sql:

CREATE MATERIALIZED VIEW mv1 BUILD IMMEDIATE
CREATE MATERIALIZED VIEW mv1 REFRESH COMPLETE
CREATE MATERIALIZED VIEW mv1 REFRESH ON SCHEDULE EVERY 2 HOUR STARTS "2023-12-13 21:07:09"
CREATE MATERIALIZED VIEW mv1 KEY(k1,k2)

For the completeness of SQL syntax, I added a simple SELECT at the end to ensure they work properly.

CREATE MATERIALIZED VIEW mv1 BUILD IMMEDIATE AS SELECT k1, k2 FROM test_table;
CREATE MATERIALIZED VIEW mv1 REFRESH COMPLETE AS SELECT k1, k2 FROM test_table;
CREATE MATERIALIZED VIEW mv1 REFRESH ON SCHEDULE EVERY 2 HOUR STARTS "2023-12-13 21:07:09" AS SELECT k1, k2 FROM test_table;
CREATE MATERIALIZED VIEW mv1 KEY(k1,k2) AS SELECT k1, k2 FROM test_table;

Since the original Doris DDL did not have Materialized Views, I referred to Materialized Views and added parsing syntax in DDLStatement.g4.

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