SLS_ACCOUNT_ID identity override for schedule events

## Feature Request

`SLS_ACCOUNT_ID` and related env var overrides only work for http event types and not schedule events. The AccountID is an identifier that would be useful for testing cross-account Cloudwatch events triggered by rate or cron schedules.

This logic appears to live at `src/events/schedule/ScheduleEvent.js`, but my feeble attempts to get this working myself have thus far failed. I though it would be as simple as adding a check for the variable and importing env (see sample below), but so far have come up empty-handed, with the auto-generated id still being used.

**Sample Code**

- file: serverless.yml

```yaml
service: my-service

plugins:
- serverless-offline

provider:
runtime: go1.x
stage: local

functions:
hello:
environment:
SLS_ACCOUNT_ID: "XXXXXXXXXXXXXXXXXXXX"
events:
- schedule: rate(1 minute)
handler: bin/hello
```

- file: src/events/schedule/ScheduleEvent.js

```js
import { createUniqueId } from '../../utils/index.js'
import { env } from 'node:process'

export default class ScheduleEvent {
account = env.SLS_ACCOUNT_ID || createUniqueId()

['detail-type'] = 'Scheduled Event'

id = createUniqueId()

region = null
}
```

**Expected behavior/code**

The presence of `env.SLS_ACCOUNT_ID` should be used as `account` rather than `createUniqueId()`

**Additional context/Screenshots**