Do not block creating compilation if bicepconfig.json on language server side

[bhsubra]

We currently don't create compilation if bicepconfig.json is invalid:

bicep/src/Bicep.LangServer/BicepCompilationManager.cs

Line 247 in d2ee05f

// this is a fatal error likely due to a code defect

We should log diagnostics and go ahead with creating compilation with default bicepconfig.json settings as user can get much of the functionality even with a malformed config file.