Weak Default Password on System VMs.

### The required feature described as a wish

**Description:** By default, CloudStack uses a hard-coded password for all System VMs.

**Affected Components:** System VMs (SSVM, CPVM, and VR)

**Impact:** An attacker who knows the default credentials, which are publicly documented, and has console access to any System VM could log in as `root`.

- On a VR: the attacker could act as a man-in-the-middle (MITM).
- On a SSVM: the attacker could tamper with templates and ISOs, and delete snapshots.
- On a CPVM: the attacker could potentially install a keylogger on noVNC sessions.

Steps to Reproduce:

- Open the Console of any System VM.
- Enter the default username `root` and password `password`.

**Recommended Remediation:** Enable randomization of System VM passwords by default, while allowing administrators to disable this behavior if needed.

**Note:** This feature already exists. Additionally, documentation improvements have been proposed to clarify how to enable and use it.

首先定位现有的 System VM 密码随机化功能，以及本 issue 中提议的文档；未指定具体文件或测试。检查该行为如何应用于 SSVM、CPVM 和 VR，包括配置默认值和退出选项。完成的标准是密码默认进行随机化，管理员仍然可以禁用该行为，并且使用方式得到清晰的文档说明。

由索引模型根据 Issue 内容生成。