Add a test of memory use when logging a lot of big images

[emilk]

Investigating #1242

RERUN_TRACK_ALLOCATIONS=1 cargo r -p test_image_memory

It turns out that when we log normal RGBA images we store the data once in the ArrowMsg, and then that data is deep-cloned when put in the store. I think it is because of this:

#[derive(Clone, Debug, PartialEq, ArrowField, ArrowSerialize, ArrowDeserialize)]
#[arrow_field(type = "dense")]
pub enum TensorData {
    U8(Vec<u8>),
    U16(Buffer<u16>),
    U32(Buffer<u32>),
    U64(Buffer<u64>),
    // ---
    I8(Buffer<i8>),
    I16(Buffer<i16>),
    I32(Buffer<i32>),
    I64(Buffer<i64>),
    // ---
    // TODO(#854): Native F16 support for arrow tensors
    //F16(Vec<arrow2::types::f16>),
    F32(Buffer<f32>),
    F64(Buffer<f64>),
    JPEG(Vec<u8>),
}

We use the ref-counted Buffer for everything except for 8-bit tensors (most images) and for jpegs.

We have a similar problem for the Mesh3D component.