Reduce double and float precision requirements on rest CSV tests (elastic#114313)

Fixes elastic/elasticsearch-serverless#2837

The failing value is `5.801464200000001`, which rounds to `5.8014642`. However, `5.8014642` is roudned to `5.801464199`.
With a precision of 7, both are truncated to `5.801464`.

Not the most elegant solution, but it works for this case, which may be a quite edgy one.

Author: ivancea

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/EsqlSpecTestCase.java

@@ -279,9 +279,9 @@ private Object valueMapper(CsvTestUtils.Type type, Object value) {
                 }
                 return values;
             } else if (value instanceof Double d) {
-                return new BigDecimal(d).round(new MathContext(10, RoundingMode.DOWN)).doubleValue();
+                return new BigDecimal(d).round(new MathContext(7, RoundingMode.DOWN)).doubleValue();
             } else if (value instanceof String s) {
-                return new BigDecimal(s).round(new MathContext(10, RoundingMode.DOWN)).doubleValue();
+                return new BigDecimal(s).round(new MathContext(7, RoundingMode.DOWN)).doubleValue();
             }
         }
         return value.toString();