Set CPS index options only when not using PIT (#137728)

PIT endpoints do not currently support CPS, and their `allowsCrossProject()`
method returns `false` anyway. This prevents the Security Action Filter from
rewriting the index expressions, and only those indices are used that are provided.
However, when the `_search` endpoint is hit with CPS enabled, along with the PIT
ID obtained previously by hitting the `_pit` endpoint, CPS index options are applied,
which causes a validation error when `TransportAction` calls `validate()`.

This change prevents the CPS index options application when PIT is found in the
request's body.

Author: pawankartik-elastic

docs/changelog/137728.yaml

@@ -0,0 +1,5 @@
+pr: 137728
+summary: Set CPS index options only when not using PIT
+area: CCS
+type: bug
+issues: []

server/src/main/java/org/elasticsearch/rest/action/search/RestSearchAction.java

@@ -245,7 +245,7 @@ public static void parseSearchRequest(
         searchRequest.routing(request.param("routing"));
         searchRequest.preference(request.param("preference"));
         IndicesOptions indicesOptions = IndicesOptions.fromRequest(request, searchRequest.indicesOptions());
-        if (crossProjectEnabled && searchRequest.allowsCrossProject()) {
+        if (crossProjectEnabled && searchRequest.allowsCrossProject() && searchRequest.pointInTimeBuilder() == null) {
             indicesOptions = IndicesOptions.builder(indicesOptions)
                 .crossProjectModeOptions(new IndicesOptions.CrossProjectModeOptions(true))
                 .build();