Move four more Enterprise-only controllers into pkg/enterprise

[caseydavenport]

Description

Second batch for CORE-13484. Four more Enterprise-only controllers move under the Enterprise tree, along with the render packages nothing in core imports.

• Application layer, egress gateway, packet capture and OpenTelemetry collector controllers, each contributed through the registration list rather than named by the core manager setup.
• Their variant checks go with them, since registration is what gates a contributed controller.
• Render code for the application layer and egress gateway moves too. The OpenTelemetry collector's stays behind until the log collector controller moves, and packet capture renders out of the top-level render package, which is its own step.

Stacked on #5273, which carries the registration seam. Review the last commit.

Related: CORE-13484

Release Note

None

[caseydavenport]

Closing in favour of #5279, which contains this commit and the rest of the stack. Semaphore's job-processing outage made merging them one at a time impractical - each squash-merge invalidated the branch above it. Your approval carried over; nothing here changed.