Migrate Uptime to new Connectors APIs in place of deprecated APIs

[gmmorris]

Following the work on #90376 we have deprecated the Connector REST APIs that refer to Connectors as Actions.

The new APIs are documented here: https://www.elastic.co/guide/en/kibana/master/actions-and-connectors-api.html

As of 8.0 the deprecated APIs will no longer be available, so this issue is to remove the usage of these APIs from Uptime.

Note that the changes cover both the routes and the parameters (to correctly follow the styleguide).

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[mikecote]

We will need this done, merged and backported before 7.15.0 feature freeze so we can remove the code in the 7.16/8.0 release cycle.

[dominiqueclarke]

We are using 2 soon to be deprecated apis. The routes are defined in x-pack/plugins/uptime/common/constants/rest_api.ts and used in x-pack/plugins/uptime/public/state/api/alerts.ts.

GET /api/actions/list_action_types
GET /api/actions

We'll need to update based on the new routes defined in #90376.

GET /api/actions/list_action_types => /api/actions/connector_types
GET /api/actions => /api/actions/connectors