Update documentation to describe manual installation for the new package structure

Problem to solve

Due to the new situation where installation packages are split into the runner and the helper images, the documentation is not up to date anymore. Specifically the following pages:

These pages need to be updated with the installation information for the helper images, as standalone installation of the runner will fail due to a hard dependency.

Further details

Intended documentation audience: Ops Engineers.

Proposal

Update the documentation with the new flow.

Who can address the issue

Anyone.

Other links/references

Relevant change regarding the packaging: !5190 (merged)

Related issues: