[backport camel-4.14.x] CAMEL-24341: camel-google-secret-manager - fix GCP vault refresh task defects - #25340

… defects (apache#25326)

* CAMEL-24341: camel-google-secret-manager - fix GCP vault refresh task defects

The GCP secret refresh task read the AWS vault configuration, so
camel.vault.gcp.secrets was never honoured. It also kept triggerReloading
as receiver state, so every message following a matching secret event
triggered another CamelContext reload, restarted the subscriber on every
period (a Google ApiService can only be started while it is NEW), and
dereferenced the secretId/eventType attributes without a null check, so a
message published on the subscription by anything else failed and was
redelivered forever.

Also aligns the javadoc of the task and of the properties function with GCP
and reuses a single ObjectMapper for secret sub-key lookups.

Signed-off-by: Andrea Cosentino <ancosen@gmail.com>

* CAMEL-24341: address review - AssertJ and package-private test conventions

Per davsclaus's non-blocking note, PubsubReloadTriggerTaskTest now uses
package-private class/@test visibility and AssertJ assertions (assertThat,
assertThatThrownBy, assertThatCode(...).doesNotThrowAnyException()). The
interface-override methods (onReload/ack/nack) stay public since they override
public API. Adds a test-scoped assertj-core dependency, not previously on the
module's test classpath.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Andrea Cosentino <ancosen@gmail.com>

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Signed-off-by: Andrea Cosentino <ancosen@gmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>