Avoid browser cache busting after Jenkins restart

Atm, the browser caches JS resources via normal cache control and expiry headers. However, the resources are all bundled as adjuncts and adjunct urls have a hash that gets changed after restart, which means all resources need to be reloaded after restart.

See can we come up with a way of loading the resources from URLs that do not change after a restart.

jamesdumay has already done some experimenting with a replacement ResourceManager. See PR-587.

Other possibilities ...

• Look at the use of AssetManager in Jenkins core
• Look at bundling resources in the plugins under the webapp dir (no hash in these URLs).

Note that this will most probably require changes to js-builder and js-modules so that we can "plug in" different resource resolution algos e.g. one specific to Blue Ocean and whatever we do above.