RATIS-2518. Make testInstallSnapshotDuringBootstrap diagnostics fail-safe.

[slfan1989]

What changes were proposed in this pull request?

This is a follow-up to RATIS-2501.

RATIS-2501 added additional diagnostics for testInstallSnapshotDuringBootstrap failures. However, the diagnostic path may access raft log state from a peer whose raft log has already been closed. When this happens, dumpClusterState() can throw a secondary IllegalStateException, which hides the original failure that the diagnostics were intended to explain.

This patch makes dumpClusterState() fail-safe by safely collecting diagnostic values. If a diagnostic value is unavailable, it is logged as unavailable: <exception> instead of throwing from the diagnostic path.

What is the link to the Apache JIRA

JIRA: RATIS-2518. Make testInstallSnapshotDuringBootstrap diagnostics fail-safe.

How was this patch tested?

Tested with:

./mvnw -pl ratis-test -am -Pgrpc-tests -Dtest=TestInstallSnapshotNotificationWithGrpc#testInstallSnapshotDuringBootstrap test

Result:

[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running org.apache.ratis.grpc.TestInstallSnapshotNotificationWithGrpc
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 6.33 s - in org.apache.ratis.grpc.TestInstallSnapshotNotificationWithGrpc
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------