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

- Stack version: 8.19.21-SNAPSHOT
- LogsDB: enabled
- 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.logs2832768637: [0] found error "Unit state changed sql/metrics-default-sql/metrics-oracle-40ab49c8-bfd6-4678-96e9-7f01ae18b4ce (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/49028

Latest failed builds:
- https://buildkite.com/elastic/integrations/builds/49092
- https://buildkite.com/elastic/integrations/builds/49170
- https://buildkite.com/elastic/integrations/builds/49243
- https://buildkite.com/elastic/integrations/builds/49335

Start with the oracle package's system test for elastic-agent logs on the memory data stream and compare the linked Buildkite failures. Investigate the ORA-12541 no-listener error; done means the oracle.memory test passes without the metricset entering a DEGRADED state.

Written by the indexing model from the issue text.