Add InlineArray Auto-Gen feature support

[sgf]

because this feature is often used together with bit-field, so it would be good to put it in the same library.

[barncastle]

Great feature idea! I've not had much exposure to Inline Arrays but this shouldn't be too difficult to implement

In terms of implementation; do you have an example use case for this? I'm wondering if this should support all integral inline arrays or just byte ones

[sgf]

I had a similar open source project. But I abandoned that project because your implementation is better.

https://github.com/sgf/BitX

public struct  MyStruct{
public byte Field1;
public byte Field2;
public short Field3;
}

public struct TestStruct1
{
    public byte BF1;
    public int BF2;
    [InlineLen(3)]
    public MyStruct  buff; //InlineLen is a custome Attribute by your library maybe u can chose a better name
}

//generated maybe like :
[System.Runtime.CompilerServices.InlineArray(3)]
public struct MyStruct_3
{
    private MyStruct _element0;

    public const int Length = 3;

    //not need to define ,because InlineArray has been implemented
    //public Span<MyStruct> GetSpan() => MemoryMarshal.CreateSpan(ref Unsafe.As<MyStruct>(ref this),3);
    //public MyStruct this[int index] {{ get => this[index]; set => this[index] = value; }}

}

[sgf]

This feature is mainly used to allow custom structures to support fixed buffers, but the official implementation is not elegant and practical. Therefore, it is necessary to combine it with a source code generator to make the code writing process simpler.

Of course, the frequency of use of this feature itself is not very high.