Queries sometimes fail when decoding progress percent in the response

[nineinchnick]

As reported in trinodb/grafana-trino#258, queries sometimes fail with:

error querying the database: trino: json: cannot unmarshal string into Go struct field stmtStats.stats.progressPercentage of type float32

The progressPercent field is declared as a float32: https://github.com/trinodb/trino-go-client/blob/master/trino/trino.go#L722, but the Trino server uses an OptionalDouble: https://github.com/trinodb/trino/blob/ca209630136eabda2449594ef2b6a4d82fb9c2e5/core/trino-main/src/main/java/io/trino/server/QueryProgressStats.java#L132

The driver should ignore invalid values in stats.