Synchronize flow.json loading behaviour

[jribbink]

Currenty, when the flow.json is initially loaded by the LS, the LS will crash if the file is invalid. However, if changes to flow.json cause a request to the LS to reload the file, then the LS will not crash but rather ignore the reloaded file & continue to use the old one. This behaviour needs to be synchronized, as it could become somewhat unclear why the user's LS diagnostics don't line up with their flow.json file, not realizing that it is due to some error.

It may be part of a more general issue that, maybe, invalid flow.json should not be a fatal error at all & the file could just be ignored?