Repair the Visual Studio installation.
I repaired Visual Studio. No success. Light bulb/Quick Actions still missing.
Delete the MEF cache. For Visual Studio 2015 it is located in the %localappdata%\Microsoft\VisualStudio\14.0\ComponentModelCache folder.
This is a little odd. I looked on my PC and could not find any such folder as the "ComponentModelCache" under VisualStudio\14.0 (or anywhere else)- perhaps this is a problem.
I did find this tool by Mads Christiensen that says it clears the MEF Cache:
I tried running it, it didn't change anything the problem still persists. (I expected it would since I don't have that folder).
Verify if you have modified any of the settings mentioned in this StackOverflow thread.
I had stumbled upon that same StackOverflow thread before posting on here. I did take another look, but this doesn't seem to be the problem either.
In summary VS2015 still is broken for me since installing Telerik. That said, I have installed VS2017 since I reported this problem and VS2017 doesn't have the same problem (although I haven't added Telerik to VS2017 yet).
I've got a couple of months of work coming up now on legacy code changes where I won't need/use Telerik, so I'm just going to stick to VS2017 without Telerik for now. Once that is done, I'll try adding Telerik to VS2017 and cross my fingers that the same thing doesn't happen. I'll let you know if 2017 has a problem when I install Telerik.
For now, I'm not worried that VS2015 is broken now that I have VS2017.
Thank you for your help.