Change onSctpOutboundPacket 3rd parameter type to SIZE_T

[stefankiesz]

Issue #, if available:
#2094

What was changed?
The 3rd parameter of the onSctpOutboundPacket function.

Why was it changed?
To match the expected pointer-function signature of the second parameter of the usrsctp_init_nothreads function as defined here in the Usrsctp library.

How was it changed?
The parameter was changed from a ULONG to a SIZE_T.

What testing was done for the changes?
Will confirm from user that this resolved the issue, and will allow for the CI to pass.

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[sirknightj]

The CI confirms that PIC's SIZE_T macro does not match the actual size_t in certain cases, and the original authors went with ULONG as a workaround.
https://github.com/awslabs/amazon-kinesis-video-streams-pic/blob/c98c2a256a7bb3dfc4db41ae26d45e28ac7eec56/src/common/include/com/amazonaws/kinesis/video/common/CommonDefs.h#L329-L338

May need to do some more digging into why the original authors didn't use:

#include <stddef.h>

typedef size_t SIZE_T;