SonarQube to phase out security hotspots

[fniessink]

See https://community.sonarsource.com/t/moving-security-hotspots-to-security-issues/180583

Timeline per Alexander's message:

In Q2, the api/hotspots will be marked as deprecated to be sure a maximum of users see it.
By the end of Q2, all new Hotspots will be actually created as Security Issues.
During Q3, existing Hotspots will be bulk migrated as Security Issues.
At this moment, the api/hotspots endpoints will return nothing.

As per our policy, we can drop a public API if its deprecation was announced at least 180 days before the drop.

I think we will drop the API, 180 days after we reach the “api/hotspots endpoints returns nothing” phase.