[x] introduce a new function called parse_essence_file_native - this should have the same interface as the existing parse_essence_file function
[x] #465
[x] add a step 0 before 1 to integration testing (see). this should parse the model using the native parser. treat this as the generated model. compare against expected model. for the rest of the file, we should continue to use the astjson parser
[ ] make step 0 conditional. use the config.toml file for this, by adding skip_native_parser=true to the file. this can be implemented by adding a new field to the struct here
parse_essence_file_native- this should have the same interface as the existing parse_essence_file functionskip_native_parser=trueto the file. this can be implemented by adding a new field to the struct hereOriginally posted by @ozgurakgun in https://github.com/conjure-cp/conjure-oxide/issues/392#issuecomment-2483362251