Provide way for plugins to know when Dalamud is done with updates

[anna-is-cute]

Heliosphere auto-updates mods on login, but Dalamud can interrupt that and cause issues by updating Heliosphere while Heliosphere is performing its own updates.

A callback fired when all plugins are done loading post-update (or immediately if auto-updates aren't on?) would help.

[anna-is-cute]

How does this work for the case when auto-update was before plugin load?

[goaaats]

Gotcha, I figured you could do that via PluginLoadReason, but I guess that would be a little unreliable/timing-dependent if people are managing plugins on the title screen. Added another thing in https://github.com/goatcorp/Dalamud/commit/ca8a05b672b7622140bfbaeb1aa1392c49ea9209.

[anna-is-cute]

Perfect :sparkles: