Refactor `cog predict` to support `--json` flag (#2404)
* Implement `cog predict --json`
This allows `cog predict` to use JSON as the input/output format which
makes it more suitable for automation such as testing.
* Support writing output file to disk
* Refactor to use same path for output processing
* Cleanup `--output` flag
* Rename write methods
* Always transform outputs
* Clean up display of outputs in cog predict
* Preserve file extensions on `list[Path]` outputs
* Only transform outputs if the prediction was successful
* Exit from `cog predict` with non-zero exit code if prediction fails
* DEBUG
* DEBUG
* Fix adding double file extension
* Fix checking if the extension is an integer
* Add test_predict_json_input integration test
* Add more integration tests
* Support - for stdin input
* Use %q for output name format
* Send error if prediction status fails
* Fix flaky file challenge test
* Fix integration tests
* Remove newline
* Just test output file in output mode
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Co-authored-by: Will Sackfield <sackfield@replicate.com>
