Efficient registration of multiple io.deephaven.plugin.Plugin

[devinrsmith]

Spawned from #2908

io.deephaven.server.jetty.jsplugin.JsPluginsZipFilesystem currently writes a manifest N + 1 times, where N is the number of JsPlugin that have been registered. This results in re-writing the whole .zip file N + 1 times. It should be possible to be more efficient about this - at least in the case of startup where we do mass registration.

More generally, it may make sense to plumb through the ability to register more than one plugin at once, ie io.deephaven.plugin.Registration.Callback#registerAll.

We do need to be careful about liveness concerns - specifically regarding io.deephaven.plugin.type.JsPlugin#copyTo, which python is responsible for managing the path w/ a @contextmanager, see py/server/deephaven/server/plugin/register.py

[devinrsmith]

Any implementation of this must not block progress for #1809