[Tests] Fix self-referencing tests

This commit adapts some test after #31044 has been merged.

Author: tlrx

modules/lang-painless/src/test/resources/rest-api-spec/test/painless/30_search.yml

@@ -439,6 +439,6 @@
                                 source: "def x = [:] ; def y = [:] ; x.a = y ; y.a = x ; return x"
 
     - match: { error.root_cause.0.type: "illegal_argument_exception" }
-    - match: { error.root_cause.0.reason: "Iterable object is self-referencing itself" }
+    - match: { error.root_cause.0.reason: "Iterable object is self-referencing itself (ScriptBytesValues value)" }
     - match: { error.type: "search_phase_execution_exception" }
     - match: { error.reason: "all shards failed" }

x-pack/qa/smoke-test-watcher/src/test/resources/rest-api-spec/test/painless/40_exception.yml

@@ -76,7 +76,7 @@
   - match: { watch_record.state: "executed" }
   - match: { watch_record.result.actions.0.status: "failure" }
   - match: { watch_record.result.actions.0.error.caused_by.caused_by.type: "illegal_argument_exception" }
-  - match: { watch_record.result.actions.0.error.caused_by.caused_by.reason: "Iterable object is self-referencing itself" }
+  - match: { watch_record.result.actions.0.error.caused_by.caused_by.reason: "Iterable object is self-referencing itself (CustomReflectionObjectHandler stringify)" }
 
   - do:
       catch: bad_request