Improve validation for data fragments for PSRP frame headers

[Anam Navied (anamnavi)]

This pull request refines the logic for handling received data fragments in the ProcessRawData method of PriorityCollection.cs. The main improvements are to the enforcement of the maximum object size limit and the order of checks, ensuring more accurate and robust processing of incoming data. These changes make the data processing logic more robust, especially in scenarios where large or incomplete data fragments are received.

Key changes to object size limit enforcement and data processing:

• The check for exceeding the maximum allowed object size (_maxReceivedObjectSize) is now performed before confirming that the complete data fragment has been received, using a new temporary variable (totalSizeToBeReceived) to avoid prematurely updating the running total. The running total (_totalReceivedObjectSizeSoFar) is only updated after the entire fragment has been received.
• The check for whether enough data has been received to process the packet (_pendingDataStream.Length < totalLengthOfFragment) has been moved after the object size limit check, ensuring that size limits are enforced even if the fragment is incomplete.
• Exception handling has been slightly improved by catching OverflowException directly (instead of System.OverflowException).

PR Summary

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Pull request overview

This PR hardens fragment receive/defragment logic in ReceiveDataCollection.ProcessRawData by enforcing the configured maximum received object size based on the fragment header as soon as it’s available (even when the fragment payload has not fully arrived yet), while avoiding prematurely mutating the running size total.

Changes:

• Computes a temporary totalSizeToBeReceived and validates it against _maxReceivedObjectSize before the “enough bytes received” check, so oversize frames are rejected early.
• Updates _totalReceivedObjectSizeSoFar only after the complete fragment is present, preventing partial fragments from inflating the running total.
• Simplifies the overflow catch to OverflowException while retaining the same behavior on arithmetic overflow.

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