Filebeat Oracle module doesn't support alert log

**Describe the enhancement:**

Alert logs contain important information about error messages and exceptions that occur during database operations.

Now oracle module supports only aud files. Please add support for alert_XXX.log where XXX=SID.

Oracle will write the alert.log file to the directory as specified by the _BACKGROUND_DUMP_DEST_ parameter. If this parameter is not set, the alert.log will be created in a directory below the value of the _DIAGNOSTIC_DEST_ parameter: _DIAGNOSTIC_DEST_/diag/rdbms/DB_NAME/ORACLE_SID/trace. If this later parameter is not set, the alert.log file is created in the _ORACLE_HOME_/rdbms/trace directory.

```
SQL> show parameter BACKGROUND_DUMP_DEST

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------------------
background_dump_dest string /app/oracle/diag/rdbms/o11gr1/o11gr1/trace
```

**Describe a specific use case for the enhancement or feature:**

We collect oracle alert log using the following config:

```
- type: log
enabled: true
paths:
- /oracle/diag/rdbms/*/*/trace/alert_*.log
multiline.pattern: '^[A-Za-z]{3}\s+[A-Za-z]{3}\s+[0-9]{1,2}\s[0-9]{2}:[0-9]{2}:[0-9]{2}\s[0-9]{4}'
multiline.negate: true
multiline.match: after
multiline.timeout: 10
```

The payload names no repository files or tests; start by locating the existing Filebeat Oracle module and its audit-file configuration. Compare its current path and multiline handling with the requested alert_XXX.log pattern, and consider the issue complete when Oracle alert logs are collected with the described multiline behavior.

Written by the indexing model from the issue text.