Remove params byte[] from System.Net.Mail (#70513)

src/libraries/System.Net.Mail/src/System/Net/Mime/QEncoder.cs

@@ -21,7 +21,7 @@ internal QEncoder(WriteStateInfoBase wsi)
         protected override void AppendEncodedCRLF()
         {
             //the encoding for CRLF is =0D=0A
-            WriteState.Append((byte)'=', (byte)'0', (byte)'D', (byte)'=', (byte)'0', (byte)'A');
+            WriteState.Append("=0D=0A"u8);
         }
 
         protected override bool LineBreakNeeded(byte b)

src/libraries/System.Net.Mail/src/System/Net/Mime/QuotedPrintableStream.cs

@@ -244,7 +244,7 @@ public int EncodeBytes(byte[] buffer, int offset, int count)
                     if (_encodeCRLF)
                     {
                         // The encoding for CRLF is =0D=0A
-                        WriteState.Append((byte)'=', (byte)'0', (byte)'D', (byte)'=', (byte)'0', (byte)'A');
+                        WriteState.Append("=0D=0A"u8);
                     }
                     else
                     {

src/libraries/System.Net.Mail/src/System/Net/Mime/WriteStateInfoBase.cs

@@ -77,10 +77,10 @@ internal void Append(byte aByte)
             _currentLineLength++;
         }
 
-        internal void Append(params byte[] bytes)
+        internal void Append(ReadOnlySpan<byte> bytes)
         {
             EnsureSpaceInBuffer(bytes.Length);
-            bytes.CopyTo(_buffer, Length);
+            bytes.CopyTo(_buffer.AsSpan(Length));
             _currentLineLength += bytes.Length;
             _currentBufferUsed += bytes.Length;
         }
@@ -90,7 +90,7 @@ internal void AppendCRLF(bool includeSpace)
             AppendFooter();
 
             //add soft line break
-            Append((byte)'\r', (byte)'\n');
+            Append("\r\n"u8);
             _currentLineLength = 0; // New Line
             if (includeSpace)
             {