Port cloudbeat to the elastic agent v2 control protocol

[cmacknz]

The Cloudbeat team attempted to migrate to the v2 control protocol but was blocked by bugs in the agent v2 branch that have now been resolved. To accelerate their migration the Beats team will attempt to migrate Cloudbeat to the v2 protocol.

The initial attempt to migrate to the v2 control protocol was made in elastic/cloudbeat#364, which includes detailed instructions and context for how to make and test the changes with Cloudbeat.

In general this migration should be similar to the other Beats we have migrated, with the exception that Cloudbeat lives outside of the primary Beats repository even though it is based on libbeat.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[cmacknz]

The Cloudbeat team will take ownership of this, closing for now.

[cmacknz]

Reopening to give us place to track our support for Cloudbeat's migration.

The most recent attempt is at elastic/cloudbeat#458 but doesn't appear to work.