[SPARK-34737][SQL] Cast input float to double in TIMESTAMP_SECONDS

### What changes were proposed in this pull request?
In the PR, I propose to cast the input float to double in the `SecondsToTimestamp` expression in the same way as in the `Cast` expression.

### Why are the changes needed?
To have the same results from `CAST(<float> AS TIMESTAMP)` and from `TIMESTAMP_SECONDS`:
```sql
spark-sql> SELECT CAST(16777215.0f AS TIMESTAMP);
1970-07-14 07:20:15
spark-sql> SELECT TIMESTAMP_SECONDS(16777215.0f);
1970-07-14 07:20:14.951424
```

### Does this PR introduce _any_ user-facing change?
Yes. After the changes:
```sql
spark-sql> SELECT TIMESTAMP_SECONDS(16777215.0f);
1970-07-14 07:20:15
```

### How was this patch tested?
By running new test:
```
$ build/sbt "test:testOnly *DateExpressionsSuite"
```

Closes #31831 from MaxGekk/adjust-SecondsToTimestamp.

Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/datetimeExpressions.scala

@@ -502,7 +502,7 @@ case class SecondsToTimestamp(child: Expression) extends UnaryExpression
       input.asInstanceOf[Decimal].toJavaBigDecimal.multiply(operand).longValueExact()
     case _: FloatType => input =>
       val f = input.asInstanceOf[Float]
-      if (f.isNaN || f.isInfinite) null else (f * MICROS_PER_SECOND).toLong
+      if (f.isNaN || f.isInfinite) null else (f.toDouble * MICROS_PER_SECOND).toLong
     case _: DoubleType => input =>
       val d = input.asInstanceOf[Double]
       if (d.isNaN || d.isInfinite) null else (d * MICROS_PER_SECOND).toLong
@@ -517,13 +517,14 @@ case class SecondsToTimestamp(child: Expression) extends UnaryExpression
       val operand = s"new java.math.BigDecimal($MICROS_PER_SECOND)"
       defineCodeGen(ctx, ev, c => s"$c.toJavaBigDecimal().multiply($operand).longValueExact()")
     case other =>
+      val castToDouble = if (other.isInstanceOf[FloatType]) "(double)" else ""
       nullSafeCodeGen(ctx, ev, c => {
         val typeStr = CodeGenerator.boxedType(other)
         s"""
            |if ($typeStr.isNaN($c) || $typeStr.isInfinite($c)) {
            |  ${ev.isNull} = true;
            |} else {
-           |  ${ev.value} = (long)($c * $MICROS_PER_SECOND);
+           |  ${ev.value} = (long)($castToDouble$c * $MICROS_PER_SECOND);
            |}
            |""".stripMargin
       })

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/DateExpressionsSuite.scala

@@ -1406,6 +1406,7 @@ class DateExpressionsSuite extends SparkFunSuite with ExpressionEvalHelper {
     checkEvaluation(
       SecondsToTimestamp(Literal(123.456789123)),
       Instant.ofEpochSecond(123, 456789000))
+    checkEvaluation(SecondsToTimestamp(Literal(16777215.0f)), Instant.ofEpochSecond(16777215))
   }
 
   test("TIMESTAMP_MILLIS") {