Various project file related fixes

[keyboardDrummer]

Description

• Improved error reporting when incorrect Boogie options are used.
• Support text document changes for a dafnyProject language in the language server. This is required for an upcoming VSCode extension change that prevents the .dfy syntax highlighting rules from being applied to dfyconfig.toml files

How has this been tested?

• Add a CLI test that uses --boogie with an argument that does not start with an option delimiter

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.