[Ryujinx.Graphics.Nvdec.FFmpeg] Address dotnet-format issues (#5370)

* dotnet format style --severity info

Some changes were manually reverted.

* Address or silence dotnet format CA1806 and a few CA1854 warnings

* Address most dotnet format whitespace warnings

* Apply dotnet format whitespace formatting

A few of them have been manually reverted and the corresponding warning was silenced

* Add comments to disabled warnings

* Simplify properties and array initialization, Use const when possible, Remove trailing commas

* Address IDE0251 warnings

* Revert "Simplify properties and array initialization, Use const when possible, Remove trailing commas"

This reverts commit 9462e4136c0a2100dc28b20cf9542e06790aa67e.

* dotnet format whitespace after rebase

* First dotnet format pass

src/Ryujinx.Graphics.Nvdec.FFmpeg/H264/H264BitStreamWriter.cs

@@ -84,9 +84,9 @@ namespace Ryujinx.Graphics.Nvdec.FFmpeg.H264
             Flush();
         }
 
-        public Span<byte> AsSpan()
+        public readonly Span<byte> AsSpan()
         {
-            return new Span<byte>(_workBuffer).Slice(0, _offset);
+            return new Span<byte>(_workBuffer)[.._offset];
         }
 
         public void WriteU(uint value, int valueSize) => WriteBits((int)value, valueSize);
@@ -118,4 +118,4 @@ namespace Ryujinx.Graphics.Nvdec.FFmpeg.H264
             WriteBits((int)value, size - 1);
         }
     }
-}
+}