compiler, runtime: Support Formatted Error Messages

Make it possible to output formatted error messages using a
flexible API that includes an ability to specify styles and
formatters.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Tests/p4rseTests/ValueTypeParserTests.swift

@@ -42,7 +42,7 @@ import TreeSitterP4
     guard case Result.Error(let e) = err else {
       assert(false, "Expected an error, but had success")
     }
-    #expect(e.format().contains("Failed to parse a statement element: Could not parse a P4 type from \(invalid_type_name)"))
+    #expect(e.msg().contains("Failed to parse a statement element: Could not parse a P4 type from \(invalid_type_name)"))
   }
 }