Make structs readonly when applicable (#4002)

* Make all structs readonly when applicable. It should reduce amount of needless defensive copies

* Make structs with trivial boilerplate equality code record structs

* Remove unnecessary readonly modifiers from TextureCreateInfo

* Make BitMap structs readonly too

Ryujinx.Graphics.Host1x/Host1xDevice.cs

@@ -9,7 +9,7 @@ namespace Ryujinx.Graphics.Host1x
 {
     public sealed class Host1xDevice : IDisposable
     {
-        private struct Command
+        private readonly struct Command
         {
             public int[] Buffer { get; }
             public long ContextId { get; }

Ryujinx.Graphics.Host1x/SyncptIncrManager.cs

@@ -7,7 +7,7 @@ namespace Ryujinx.Graphics.Host1x
     {
         private readonly SynchronizationManager _syncMgr;
 
-        private struct SyncptIncr
+        private readonly struct SyncptIncr
         {
             public uint Id { get; }
             public ClassId ClassId { get; }