feat(core): expose loaded plugins

[brusdev]

The loaded plugins include the context path required to get plugin resources, i.e. AcriveMQ Artemis clould use the loaded plugins to avoid reloading them: apache/activemq-artemis#3765

[tadayosi]

Hmm, I still don't get why we need this. The PluginServlet and PluginRegistry in hawtio/hawtio are what we provide for users and other plugins.

[brusdev]

@tadayosi indeed the current ActiveMQ Artemis branding plugin use PluginServlet to get the plugin list, see https://github.com/apache/activemq-artemis/blob/main/artemis-hawtio/activemq-branding/src/main/webapp/plugin/js/brandingPlugin.js#L37

When a user accesses the console the PluginServlet is requested twice the first time from hawtio PluginLoader and the second time from ActiveMQ Artemis branding plugin.

This change is just to avoid the second request of PluginServlet from ActiveMQ Artemis branding plugin and reuse the outcome of the first request of PluginServlet from hawtio PluginLoader.

[tadayosi]

@brusdev Thanks. It makes sense. It shouldn't be harmful to have the plugins loaded from hawtioPluginLoader accessible from outside.