Remove errant std::move in creds code (#27751)

* remove move

* add test case

src/core/lib/security/credentials/composite/composite_credentials.cc

@@ -147,7 +147,7 @@ void grpc_composite_call_credentials::push_to_inner(
   auto composite_creds =
       static_cast<grpc_composite_call_credentials*>(creds.get());
   for (size_t i = 0; i < composite_creds->inner().size(); ++i) {
-    inner_.push_back(std::move(composite_creds->inner_[i]));
+    inner_.push_back(composite_creds->inner_[i]);
   }
 }
 

test/core/end2end/fuzzers/api_fuzzer_corpus/testcase-4953856886308864

@@ -0,0 +1,46 @@
+actions {
+  create_channel {
+    target: "unix::\360,\206=\211::::::::::6::::::::::::,:::\354\327:::::::::::::::::::::::::174515::::::::::::::::::::174515:::::::::::::::::, \310\013::::::, \310/::::::::::::::::::::::\177::::::::::::::::::::::::, \310/\032::travel/flights/summary/proto/fac::::::::, \310/\032::::::::::::::74515::::::::::::::\251:::, \310/::::::, \310/:::::::8c\017\303:::::::::::\177::::::::::::::::::::::::, \310/\032::::::::::, \310/\032::::::::::::::::::::::::::::::::::::::::::::::::::?:::::::::::::::::::::::::;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::?:::::::::::::::::::::::::;::::::::::::::"
+    channel_creds {
+      composite_channel_creds {
+        channel_creds {
+          composite_channel_creds {
+            channel_creds {
+              composite_channel_creds {
+                channel_creds {
+                  ssl_channel_creds {
+                  }
+                }
+              }
+            }
+            call_creds {
+              composite_call_creds {
+                call_creds {
+                  composite_call_creds {
+                    call_creds {
+                      access_token: ""
+                    }
+                    call_creds {
+                      iam {
+                      }
+                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+        call_creds {
+          composite_call_creds {
+            call_creds {
+              access_token: ""
+            }
+          }
+        }
+      }
+    }
+  }
+}
+actions {
+  check_connectivity: true
+}