Make shader error display in Editor always up-to-date

Due to Editor - runtime renderer separation, there is no synchronisation between editor panel updates and renderer-side shader compilation. Occasionally this means that Editor shows outdated shader compilation error status, as Editor panels are updated before shader compilation has been triggered (or finished).

We can either implement signaling from runtime to Editor to indicate shader compilation completeness, or simply implement a deferred shader error update in Project and Inspector panels.

Latter option is probably preferrable, as implementing a feedback signaling channel just for displaying shader errors is bit excessive.