[WIP] Port hardsubx classifier

[shashwat1002]

Starting port of the classifier module.

[shashwat1002]

@PunitLodha awaiting feedback before I continue here because I have taken certain liberties.

The get_ocr_text_wordwise has a memory leak because it gives ownership of a Rust originating string to the C caller. According to documentation of CString it has to be deallocated using from_raw. That can only be done when the callers above have been ported. Therefore, I'm leaving that in for now. I might have to do it for the other functions in this module as well. Therefore, please take a look before I continue.

[PunitLodha]

Logic seems fine. You can continue with the work. There are a few unwraps/panics and formatting issues, which can be reviewed later

[shashwat1002]

@PunitLodha

The classifier's porting is done. Please check

Note the currently I'm using the binding definition for AVPacket as opposed to ffmpeg_sys_next's I realised that it'll be better to make that change after this is merged.