[improve] PIP-467: Convert remaining modules logging from SLF4J to slog - #25511

…mmands

Follow-up to the review on apache#26480, pulsar-client half.

- `ProducerSocket.onMessage` had lost the `if (this.result != null)` guard, so a
  text frame arriving outside a pending send would NPE on the Jetty callback
  thread where it used to be ignored. Restores the guard and the pre-split log
  text ("Received ack" with attr `ack`); the version in the split was a
  hand-rendering of the pre-apache#25511 slf4j format string. Also drops the dead
  `throws InterruptedException` on `onConnect`, and comments the two deliberate
  changes in the same class: `send()` installs the completion future before
  `sendText(...)` (the old order let an ack complete the previous future and
  hang the caller for the full 30s), and `close()` null-checks the session that
  `onClose` clears.

- `consume-v4`'s `--start-timestamp` seek and `--end-timestamp` filter were only
  covered by their rejection messages: deleting either line left every test
  passing, though timestamp seek is the stated reason the command exists. Adds
  `PulsarClientToolTest.testConsumeV4StartAndEndTimestamp`, which pins both
  against a real observed publish time. Mutation checked: deleting either line
  fails it.

- `CmdProduceV4.nativeAvroSchemaOrNull` returned null for an Avro schema with no
  native definition, which would ship the raw JSON text as the payload; the
  pre-apache#25917 command threw. Throws again. Not reachable from any current CLI
  invocation, but the invariant is worth keeping explicit.

- `PulsarClientTool.buildV4ClientBuilder`: removes the unreachable
  "proxy-protocol must be provided with proxy-url" throw — `updateConfig()` is
  the `preRun()` hook and already returns 1 for that case before the supplier
  that reaches this method is even created, and `ClientBuilderImpl` re-checks it.
  Keeps the outer `isNotBlank` guard, which unlike the V5 path is load-bearing
  here because this builder uses `loadConf()`. Documents why `serviceUrl` and
  `tlsTrustCertsFilePath` are applied unconditionally.

- Deletes `AbstractCmdReadCommand.startMessageId()` and both overrides: never
  called, `webSocketStartMessageId()` is the one in use.

- `TestCmdConsume` sets `subscriptionName` directly instead of reflecting into
  it; the field is protected and the test is in the same package.

- `CmdV4CommandsTest` imports the `java.util` types its helper used inline.