Support parsing Doris SYNC/DESC syntax

[ccxxxyy]

for #31479

official document:

• https://doris.apache.org/docs/4.x/sql-manual/sql-statements/data-modification/load-and-export/SYNC
• https://doris.apache.org/docs/4.x/sql-manual/sql-statements/table-and-view/table/DESC-TABLE

Changes proposed in this pull request:

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[ccxxxyy]

In the Doris documentation, SYNC is treated as a reserved keyword.