[Stack 8.19.21-SNAPSHOT] [oracle] Failing test daily: system test: (elastic-agent logs - memory) in oracle.memory

- Stack version: 8.19.21-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.logs3113895911: [0] found error "Unit state changed sql/metrics-default-sql/metrics-oracle-96880f44-d668-46da-ae55-4915928406f2 (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/49027

Latest failed builds:
- https://buildkite.com/elastic/integrations/builds/49093
- https://buildkite.com/elastic/integrations/builds/49169
- https://buildkite.com/elastic/integrations/builds/49242
- https://buildkite.com/elastic/integrations/builds/49336

Start with the latest failed Buildkite runs and the oracle.memory system test, focusing on the elastic-agent logs memory case and its sql.query connection failure. Trace why the Oracle listener is unavailable in these runs; done means the oracle.memory system test no longer reports ORA-12541.

Written by the indexing model from the issue text.