OpenAPI: Retry REST test server start on wrapped BindException

[wombatu-kun]

Summary

RESTServerExtension#beforeAll starts an embedded REST catalog server for tests on an OS-assigned free port (RCKUtils.findFreePort() opens ServerSocket(0), reads the port, and closes it). Because Jetty binds to that port only later in httpServer.start(), there is a TOCTOU window in which a parallel test JVM fork can grab the same ephemeral port, producing java.net.BindException: Address already in use.

PR #13017 added a 10-attempt retry to paper over that window, but it never fires. It re-rolls the port only inside catch (BindException e), while Jetty surfaces the failure as a java.io.IOException("Failed to bind to ...") whose cause is the real BindException. Since IOException is not a BindException, control falls through to the generic catch (Exception e), which rethrows immediately with no retry, so a single lost port race aborts the whole test class with initializationError.

This changes the catch to detect a bind failure by scanning the exception's cause chain, so the existing retry actually re-rolls the port on a wrapped BindException. The deeper TOCTOU window is inherent to probe-then-bind and is left as-is; retry is the agreed mitigation. This is a follow-up to the two earlier attempts at this same flakiness: #13017 (add the retry) and #13992 (enable SO_REUSEPORT, which only covers the TIME_WAIT case, not an active bind by another fork).

Observed as a flaky failure of TestAddFilesProcedure > initializationError in the spark-tests (17, 3.5, 2.12, extensions) job (which then fail-fast cancels the sibling core jobs), e.g. on the unrelated PR #17065: https://github.com/apache/iceberg/actions/runs/28645321282/job/84950457116

java.lang.RuntimeException: Failed to start REST server
    at org.apache.iceberg.rest.RESTServerExtension.beforeAll(RESTServerExtension.java:78)
Caused by: java.io.IOException: Failed to bind to 0.0.0.0/0.0.0.0:35673
    at org.apache.iceberg.rest.RESTCatalogServer.start(RESTCatalogServer.java:130)
Caused by: java.net.BindException: Address already in use

Testing

Added TestRESTServerExtension covering the cause-chain detection: the exact CI shape (an IOException wrapping a BindException, asserting it is not itself a BindException so a direct catch would miss it), a direct BindException, non-bind failures, and null.