Add fingerprinting for entire payloads

What does this MR do?

This adds automatic fingerprinting for Alert Management Alerts.

This is a GitLab Premium feature.

How it works:

1. When the user sends a payload through the API, and the user has a GitLab Premium or above license,
2. We generate a fingerprint using the payload, excluding the start_time and hosts params (as these are often changing)
3. If another alert is found with this fingerprint, we increment the alert count. This is the same logic as when a user provided fingerprint is provided in the payload(https://docs.gitlab.com/ee/user/project/integrations/generic_alerts.html#customizing-the-payload).

We do the following to ensure the payload fingerprint is calculated correctly:

• Convert any nested keys into inline keys
• Sort the inline keys, so ensure each duplicate hash generates the same SHA
• Check to see if the hash values are are present

As this is currently behind a FF, no changelog or docs are required for this MR.

FF removal issue: #224113 (closed)

Screenshots

Alert list

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry feature flag
• [-] Documentation (if required) feature flag
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Refs #214557 (closed)