…ttack discovery scheduling feature flags by default (elastic#228327)

## [AI4DSOC] [Attack discovery] Enable the _Attack discovery alerts_ and _Attack discovery scheduling_ feature flags by default

This PR programmatically enables (by default) the [Attack discovery alerts](elastic#218906) and [Attack discovery scheduling](elastic#217917) feature flags.

Together, these features enable:

- Persistence of Attack discoveries as alerts
- Scheduling Attack discoveries, with support for actions, and cases integration
- Open | Acknowledged | Closed workflow statuses for Attack discoveries
- A new UI for searching and sharing previously created Attack discoveries

This PR enables the feature flags by default, as illustrated by the following screenshot:

![attack_discovery_after](https://github.com/user-attachments/assets/b3ace302-d641-4fde-9848-a00603d7c46c)

_Above: Attack discovery alerts and scheduling are enabled by default_

When the feature flags are manually _disabled_, the Attack discovery page looks like the following screenshot:

![feature_flag_off](https://github.com/user-attachments/assets/bdc9e4c1-26be-4b01-83d0-2f0cef59c863)

_Above: The feature flags are manually disabled in the screenshot above_

### Desk testing

1) **Remove** any old feature flag entries that may be present in `config/kibana.dev.yml`, like the following example:

```yaml
feature_flags.overrides:
  securitySolution.attackDiscoveryAlertsEnabled: false
  securitySolution.assistantAttackDiscoverySchedulingEnabled: false
```

2) Start a local development instance of Kibana

3) Navigate to Security > Attack discovery

**Expected result**

- The call to action buttons at the top of the page include the `Run` and `Schedule` buttons, as illustrated by the following animated gif:

![03_cta_tooltips](https://github.com/user-attachments/assets/f43b39dc-a184-43db-a812-16e97798186f)

- The layout of page is similar to the following screenshot:

![attack_discovery_after](https://github.com/user-attachments/assets/b3ace302-d641-4fde-9848-a00603d7c46c)

4) Disable the feature flags by adding the following entries to `config/kibana.dev.yml`:

```yaml
feature_flags.overrides:
  securitySolution.attackDiscoveryAlertsEnabled: false
  securitySolution.assistantAttackDiscoverySchedulingEnabled: false
```

5) Once again, navigate to Security > Attack discovery

**Expected results**

- The call to action button at the top of the page is `Generate`
- The `Schedule` call to action button does NOT appear
- The layout of the page is similar to the following screenshot:

![feature_flag_off](https://github.com/user-attachments/assets/bdc9e4c1-26be-4b01-83d0-2f0cef59c863)

(cherry picked from commit 90ed7a1)