ESQL: Enable docs for ROUND_TO (elastic#128378)

Plug the docs in for ROUND_TO.

Author: nik9000

docs/reference/query-languages/esql/_snippets/functions/layout/round_to.md

@@ -16,6 +16,7 @@
 * [`PI`](../../functions-operators/math-functions.md#esql-pi)
 * [`POW`](../../functions-operators/math-functions.md#esql-pow)
 * [`ROUND`](../../functions-operators/math-functions.md#esql-round)
+* [`ROUND_TO`](../../functions-operators/math-functions.md#esql-round_to)
 * [`SCALB`](../../functions-operators/math-functions.md#esql-scalb)
 * [`SIGNUM`](../../functions-operators/math-functions.md#esql-signum)
 * [`SIN`](../../functions-operators/math-functions.md#esql-sin)

docs/reference/query-languages/esql/_snippets/lists/math-functions.md

@@ -66,6 +66,9 @@ mapped_pages:
 :::{include} ../_snippets/functions/layout/round.md
 :::
 
+:::{include} ../_snippets/functions/layout/round_to.md
+:::
+
 :::{include} ../_snippets/functions/layout/scalb.md
 :::
 

docs/reference/query-languages/esql/functions-operators/math-functions.md

@@ -20,6 +20,8 @@
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
 import org.elasticsearch.xpack.esql.expression.function.Example;
+import org.elasticsearch.xpack.esql.expression.function.FunctionAppliesTo;
+import org.elasticsearch.xpack.esql.expression.function.FunctionAppliesToLifecycle;
 import org.elasticsearch.xpack.esql.expression.function.FunctionInfo;
 import org.elasticsearch.xpack.esql.expression.function.Param;
 import org.elasticsearch.xpack.esql.expression.function.scalar.EsqlScalarFunction;
@@ -50,8 +52,13 @@ public class RoundTo extends EsqlScalarFunction {
 
     private DataType resultType;
 
-    @FunctionInfo(returnType = { "double", "integer", "long", "date", "date_nanos" }, description = """
-        Rounds down to one of a list of fixed points.""", examples = @Example(file = "math", tag = "round_to"))
+    @FunctionInfo(
+        returnType = { "double", "integer", "long", "date", "date_nanos" },
+        description = """
+            Rounds down to one of a list of fixed points.""",
+        examples = @Example(file = "math", tag = "round_to"),
+        appliesTo = { @FunctionAppliesTo(lifeCycle = FunctionAppliesToLifecycle.COMING, version = "8.19.0/9.1.0") }
+    )
     public RoundTo(
         Source source,
         @Param(