Always use 1d locations in metadata

[keyboardDrummer]

Changes

• Remove file2dRange (r: Strata.File2dRange) from MetaData, since Strata's ASTs should contain 1d positions
• Use DiagnosticModel instead of Format in much of the code to represent diagnostics. DiagnosticModel keeps the error location and error message separated, so the location can be converted to 2d later on.

Future work

• There are many locations where an error is created but location information is not available. These use deprecated methods like DiagnosticModel.fromFormat to create a DiagnosticModel without a location. These locations should be updated so they create diagnostics with locations.
• Allow DiagnosticModel to contain error codes, so the front-ends can translate the diagnostics as they desire
• Allow DiagnosticModel to contain multiple locations and messages

Testing

• Refactoring, uses existing tests

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[atomb]

I second @MikaelMayer's questions, but don't have any of my own to add.