cache power reports

Check version

• I'm running the latest version of Path of Building and I've verified this by checking the changelog

Check for duplicates

• I've checked for duplicate issues by using the search function of the issue tracker

Is your feature request related to a problem?

Power reports are extremely slow to generate, and they are often switched between even without modifying anything.

Describe the solution you'd like

A very simple cache would wok wonders for many use cases. You don't even need to be smart about caching sub-graph, just invalidate on modification. You could also keep a map of the build code to results for when edits are done and reverted often. I do that a lot, but I'm not sure how others use it. These are both pretty low impact changes I would think.

Describe alternatives you've considered

Rewrite in c++ probably isn't a great solution.

Additional context

Also, some progress indicator in a window footer for how much computation still needs to be done would be nice.

Das Issue nennt keine Dateien, Tests oder einen Einstiegspunkt. Beginne damit, den Ablauf zur Generierung von power-report zu lokalisieren und zu bestimmen, wie Änderungen am Build erkannt werden; bewerte anschließend Caching und den angeforderten Fortschrittsindikator getrennt. Als abgeschlossen gilt die Aufgabe, wenn wiederholte, unveränderte Reports unnötige Berechnungen vermeiden und die verbleibende Arbeit durch geeignete Validierung abgedeckt ist.