[ManickaP]

Note

This PR was created with the assistance of GitHub Copilot.

Implements the API-approved design from dotnet#90281.

Changes

Adds a settable Priority property (byte) and a DefaultPriority constant (0x7F) to QuicStream, per the approved API shape:

namespace System.Net.Quic;

public partial class QuicStream
{
    public const byte DefaultPriority = 0x7F;
    public byte Priority { get; set; }
}

• Getter returns the cached field value (no P/Invoke).
• Setter calls SetMsQuicParameter(QUIC_PARAM_STREAM_PRIORITY, (ushort)((value << 8) | 0xFF)) to translate the byte range to MsQuic's ushort range.
• Throws ObjectDisposedException after disposal.

Tests

Four new tests in QuicStreamTests.cs:

• Priority_DefaultValue — both client/server streams default to 0x7F
• Priority_SetGet (Theory) — roundtrip for min, 1, default, max values
• Priority_SetMultipleTimes — changing priority multiple times
• Priority_ThrowsAfterDispose — ObjectDisposedException after disposal

All existing and new tests pass.

Fixes dotnet#90281