Quantized GGUF style (#1523)

* Metal quantized modifications proposal.

- Add a device param, wherever needed.
- Create new QMetal storage thing that implements QuantizedType.
- Update everywhere needed.

Fix Python.

Fixing examples.

Fix: fmt + clippy + stub.

Moving everything around.

Only missing the actual implems.

Fixing everything + adding dequantized kernels.

More work.

Fixing matmul.

Fmt + Clippy

Some clippy fixes.

Working state.

Q2K Metal -> Bugged (also present in GGML).
Q4K CPU -> Bugged (present previously, new test catch it).
Q5K CPU -> Bugged (present previously).
Q8_1 Both -> Never really implemented it seems
Q8K metal -> Never implemented in metal

Fixing Q2K bug (present in ggml).

* Cleanup.

* Fix the rebase.

* Removing the fences speeds everything up and *is* correct this time...

* Cleanup the fence.

* After rebase.

* Bad code removal.

* Rebase after phi2 merge + fix replit default to CPU.

* Making the CI happy.

* More happy tests.

---------

Co-authored-by: Nicolas Patry <nicolas@Nicolass-MacBook-Pro.local>

candle-nn/examples/cpu_benchmarks.rs

@@ -222,7 +222,10 @@ impl Benchmark for QMatMul {
     type RunResult = Tensor;
     fn preprocess() -> Result<Self::PreProcessData> {
         let zeros = vec![candle::quantized::k_quants::BlockQ4_0::zeros(); 4096 * 11008 / 32];
-        let mm = candle::quantized::QTensor::new(zeros, (4096, 11008))?;
+        let mm = candle::quantized::QTensor::new(
+            candle::quantized::QStorage::Cpu(Box::new(zeros)),
+            (4096, 11008),
+        )?;
         let mm = candle::quantized::QMatMul::from_qtensor(mm)?;
         let arg = Tensor::randn(0f32, 1., (128, 11008), &Device::Cpu)?;
         Ok((mm, arg))