json: markers reported on start for files not opened

[vince-fugnitto]

Description

When theia is used as a workspace, I noticed that json warnings are outputted (.theia), despite any of the files being opened. Is this the intended behavior? When verifying the same use case in VS Code, no warnings are present in the problems view:

Steps to Reproduce

1. start the application (better to start with a fresh port and no local storage)
2. open theia as a workspace (no files should be opened)
3. the problems view outputs warnings for json files under .theia

[akosyakov]

@vince-fugnitto probably we store markers between sessions, do you think it is bad? misleading? or helpful since it shows you what is really wrong faster?

[vince-fugnitto]

@vince-fugnitto probably we store markers between sessions, do you think it is bad? misleading? or helpful since it shows you what is really wrong faster?

I felt that, especially since they are warnings in this case, that displaying the markers on startup is a bit noisy. I noticed in VS Code this same behavior is not present, the markers are only visible when first opening the file and not on startup. I am surprised it'd store the markers between sessions, I made sure to start at a different port and also delete my local history. That is of course my own opinion, I wonder what others might think.

cc @marcdumais-work @lmcbout @marechal-p