[FEATURE] Return alert value information in bucket level ctx for notification messages

[AWSHurneyt]

Is your feature request related to a problem?
Currently, alerts do not expose the value that triggered the trigger condition in the asTemplateArgs function. This prevents notification messages from including that info.

For example, if a bucket monitor is configured to query an index with the following type of document, and generate an alert when the value field is < 50, we cannot currently include that triggering value in the notification body.

POST test-index-1/_doc?pipeline=test-timestamp
{
  "name": "Thomas",
  "value": 10
}

What solution would you like?
Expose the triggering value in the ctx of alerts. This information can be helpful for consumers of notifications for determining what actions to take to resolve an alert.

Additional context
Related issue #1299

[AWSHurneyt]

Closing in favor of #1401