fix: Resolve integer overflow in Load API file decoding

[pskiran1]

What does the PR do?

This PR addresses the following issue:

• When large data is sent to /v2/repository/models/<model_name>/load, the server converts the param_len variable from size_t to const int to pass it to base64_decode_block. This conversion can cause an integer overflow in base64_decode_block, leading to a server crash with a segmentation fault.
• A similar issue occurs with /v2/cudasharedmemory/region/{}/register when large data is sent for the raw_handle parameter.

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Test plan:

• CI Pipeline ID: 20358255

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Background

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• closes GitHub issue: #xxx