fix: add support for direct file bytes

[tanzimCohere]

The PR introduces changes to the process_file function in the parser.py module, enhancing file processing and error handling.

• The process_file function now accepts additional parameters, including file_id, content_type, parser_config, metadata_config, and custom_context.
• A new function, _process_file_bytes, is introduced to handle file processing. It takes params, filename, file_bytes, and custom_context as arguments.
• The if statement checking the file size has been moved from the process_file function to the _process_file_bytes function.
• The files dictionary in the self.session.post method now uses file_bytes instead of doc.filebytes for the file content.

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[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
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[benrules3]

The direction looks good here! Would just request a test case and a manual version bump to 0.19.0.

Then if you confirm this works for you, we should be good to approve