[Stack 8.19.19-SNAPSHOT] [oracle] Failing test daily: system test: (elastic-agent logs - memory) in oracle.memory

- Stack version: 8.19.19-SNAPSHOT
- Package: oracle
- Failing test: system test: (elastic-agent logs - memory)
- DataStream: memory
- Owners:
- @elastic/obs-infraobs-integrations

Failure:
```
test case failed: one or more errors found while examining elastic-agent.logs3317869869: [0] found error "Unit state changed sql/metrics-default-sql/metrics-oracle-59c67ce6-aca7-4c9f-bdd0-e27d32852607 (HEALTHY->DEGRADED): Error fetching data for metricset sql.query: cannot open connection: testing connection: user=\"sys\" standalone params={authMode:2 connectionClass: connectionClassLength:0 purity:0 newPassword: newPasswordLength:0 appContext: numAppContext:0 externalAuth:0 externalHandle: pool: tag: tagLength:0 matchAnyTag:0 outTag: outTagLength:0 outTagFound:0 shardingKeyColumns: numShardingKeyColumns:0 superShardingKeyColumns: numSuperShardingKeyColumns:0 outNewSession:0}: ORA-12541: TNS:no listener"
```

First build failed: https://buildkite.com/elastic/integrations/builds/46081

Latest 5 failed builds:
- https://buildkite.com/elastic/integrations/builds/46710
- https://buildkite.com/elastic/integrations/builds/46801
- https://buildkite.com/elastic/integrations/builds/46859
- https://buildkite.com/elastic/integrations/builds/46920
- https://buildkite.com/elastic/integrations/builds/47003

Start with the failing oracle.memory system test and the linked Buildkite builds, comparing the first failure with the latest five failures. Investigate the ORA-12541 “TNS:no listener” connection error and the elastic-agent logs; done means the test can connect to Oracle and the memory DataStream test passes reliably.

Written by the indexing model from the issue text.