docs,ci: updates to ci docs
docs,ci: updates to ci docs

this commit moves the Jenkins related portion of the docs higher, as
they typically will be what users are looking for first.

it also makes a specific subsection for retriggering jobs.

Signed-off-by: Louis DeLosSantos <e7ae6d6e1769b56e461abca13c275680721e78d7@isovalent.com>

michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium