Lazy plugin / node initialization

[oxysoft]

Hello! I believe it may be possible to build a lightweight manifest of the nodes that each plugin provides in order to massively speed up the initialization of the core. When a workflow with missing nodes is loaded, we look up the manifest to see if it's in an unloaded plugin. The manifest rebuild could be manual (and the lazy loading feature could be optional as a whole for those who don't wanna worry about it) In theory if the plugin manager triggers a manifest rebuild whenever a plugin is installed or rebuilt, then it should always be up-to-date.

What do you think?