[Bug] DUMP keyword cannot be used as an identifier

`DUMP` is a lexer keyword used by `PLAN REPLAYER DUMP`, but it was never added to the `nonReserved` list in the Nereids grammar. As a result, `dump` cannot be used as an ordinary identifier — e.g. a column, table, alias, or CTE named `dump` fails to parse:

```sql
SELECT dump FROM t; -- parse error
SELECT 1 AS dump FROM t; -- parse error
```

In older versions (e.g. 2.1) `dump` worked as an identifier, so this is a backward-compatibility regression for users who have objects named `dump`. `DUMP` should be a non-reserved keyword.

Locate the Nereids grammar's nonReserved list and the lexer rule used by PLAN REPLAYER DUMP. Verify the existing SELECT examples and related parser tests, if present; done means DUMP remains usable for PLAN REPLAYER DUMP while dump parses as a column, table, alias, and CTE identifier.

Written by the indexing model from the issue text.