[Vectra]: New Stream dataset

### Integration Name

Vectra Detect [packages/vectra_detect]

### Dataset Name

stream

### Integration Version

1.14.0

### Agent Version

N/A

### OS Version and Architecture

N/A

### User Goal

Collect logs from Vectra Stream currently only supports detect

https://www.vectra.ai/resources/vectra-stream-overview

### Existing Features

N/A

### What did you see?

N/A

### Anything else?

_No response_

Start in packages/vectra_detect and read the existing Detect dataset configuration to understand how this integration collects logs. Add a Stream dataset for Vectra Stream alongside the current Detect support, using the linked Vectra Stream overview for context. Done means the package supports collecting Stream logs without removing Detect support.

Written by the indexing model from the issue text.