Do not throw in task enqueued by CancellableRunner (elastic#112780)

CancellableThreads#excute can throw runtime exception including
cancellation. This does not work with AbstractThrottledTaskRunner which
expects enqueued task to _not_ throw. This PR catches any runtime
exception from CancellableThreads and hand it back to the original
runnable.

Resolves: elastic#112779

Author: ywangd

muted-tests.yml

@@ -211,9 +211,6 @@ tests:
 - class: org.elasticsearch.repositories.blobstore.testkit.integrity.RepositoryVerifyIntegrityIT
   method: testCorruption
   issue: https://github.com/elastic/elasticsearch/issues/112769
-- class: org.elasticsearch.repositories.blobstore.testkit.integrity.RepositoryVerifyIntegrityIT
-  method: testTransportException
-  issue: https://github.com/elastic/elasticsearch/issues/112779
 - class: org.elasticsearch.script.StatsSummaryTests
   method: testEqualsAndHashCode
   issue: https://github.com/elastic/elasticsearch/issues/112439

x-pack/plugin/snapshot-repo-test-kit/src/main/java/org/elasticsearch/repositories/blobstore/testkit/integrity/RepositoryIntegrityVerifier.java

@@ -934,7 +934,11 @@ public void onResponse(Releasable releasable) {
                         if (cancellableThreads.isCancelled()) {
                             runnable.onFailure(new TaskCancelledException("task cancelled"));
                         } else {
-                            cancellableThreads.execute(runnable::run);
+                            try {
+                                cancellableThreads.execute(runnable::run);
+                            } catch (RuntimeException e) {
+                                runnable.onFailure(e);
+                            }
                         }
                     }
                 }