[Security Solutions] Add PLI authorisation for Cases Connector (#161343)

## Summary

* Create a new capability called `cases_connectors` which will control
the access to the cases connector feature. Note that for users to have
access to this feature they also need to be authorized for cases feature
and actions feature.
* Create a new API tag `casesGetConnectorsConfigure` to restrict access
to the Get Connectors APIs.

## Authorization

For the authorization of users we use a) a new UI capability b) a new
API access tag and c) the existing Cases RBAC. The Cases feature
privilege in Security solution is constructed based on the configuration
provided by the security serverless plugin. The UI capability, the API
tag, and the cases operations will be added/removed depending on the
configuration.

### UI capability

We include the `CASES_CONNECTORS_CAPABILITY` which will be used by the
UI to show/hide various UI components responsible for the case
connectors feature.

### APIs

There are two APIs that use connectors in Cases. The [Get Connectors
API](https://www.elastic.co/guide/en/kibana/current/case-apis.html#findCaseConnectors)
which returns all supported connectors by Cases and the [Push Case
API](https://www.elastic.co/guide/en/kibana/current/case-apis.html#pushCaseDefaultSpace)
that push a case to an external service.

#### Get Connectors API

The Get Connectors API does not interact with any of the cases' saved
objects. It uses the `actionsClient`, provided by the actions plugin, to
get all connectors and filter out the ones supported by cases. For that
reason, an API tag called `GET_CONNECTORS_CONFIGURE_API_TAG` is added to
the API to control access. If the user has access to any of the Cases
kibana privilege features (Security, Observability, or Stack) it will
have access to the API. This is an expected behavior and in the Security
serverless project, only one Case feature will be available.

#### Push Case API

The Push Case API already authorizes users by using the Cases RBAC. The
user should have the `push` operation set in the Cases Kibana feature
privilege to be able to use the API.

## Permissions

<meta charset="utf-8"><b style="font-weight:normal;"
id="docs-internal-guid-d1fea174-7fff-4f03-ed2e-9fc3ad3ed789"><div
dir="ltr" style="margin-left:0pt;" align="left">

Cases | Actions | Case Connectors | Outcome
-- | -- | -- | --
read | all | all | See the connector but cannot edit (current behavior)
read | all | none | Hide the connectors in Cases
read | read | all | See the connector but cannot edit (current behavior)
read | read | none | Hide the connectors in Cases
all | all | all | Full access
all | all | none | Hide the connectors in Cases
all | read | all | See the connector but cannot edit (current behavior)
all | read | none | Hide the connectors in Cases

</div><br /></b>

When the Actions is set to `none` all connector features are hidden

### How to test it?
#### ESS
* Run ESS and check if it still works as expected for all combinations
of cases and actions permissions.

#### Serverless
* Run Serverless with security essentials (serverless.security.yml) and
check if it works as expected for all combinations of cases and actions
permissions.

```
xpack.serverless.security.productTypes:
  [
    { product_line: 'security', product_tier: 'essentials' }
  ]


```
* Run Serverless with security complete (config/serverless.security.yml)
and check if it works as expected for all combinations of cases and
actions permissions.
```
xpack.serverless.security.productTypes:
  [
    { product_line: 'security', product_tier: 'complete' },
  ]
 
 ```



### Checklist

Delete any items that are not applicable to this PR.

- [x] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios

---------

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Christos Nasikas <christos.nasikas@elastic.co>

x-pack/plugins/exploratory_view/public/components/shared/exploratory_view/header/add_to_case_action.test.tsx

@@ -110,6 +110,7 @@ describe('AddToCaseAction', function () {
           update: false,
           delete: false,
           push: false,
+          connectors: false,
         },
       })
     );