next ollama runner (#7913)

feat: add new Ollama engine using ggml through cgo

This change introduces a new way to run pretrained models. It introduces 3 high level interfaces and a bunch of smaller helper interfaces to facilitate this.

- `model.Model` defines the interface for a model architecture. Models such as `llama` and `mllama`, which are provided as examples, can implement the model's forward propagation in the `Forward` method. This method will be called to generate completions. This interface can be found in `model/model.go`
- `ml.Backend` defines the interface for a backend tensor library, in this case `ggml`. Among other things, a Backend is responsible for loading a pretrained model into hardware (GPU, CPU, etc) and providing an interface for Models to access loaded tensors. This interface can be found in `ml/backend.go`
- `ml.Tensor` defines the interface for a tensor and tensor operations

This is the first implementation of the new engine. Follow up PRs will implement more features:

- non-greedy sampling (#8410)
- integration with Ollama and KV caching (#8301)
- more model support (#9080) with more coming soon

Co-authored-by: Bruce MacDonald <brucewmacdonald@gmail.com>

fs/util/bufioutil/buffer_seeker.go

@@ -0,0 +1,34 @@
+package bufioutil
+
+import (
+	"bufio"
+	"io"
+)
+
+type BufferedSeeker struct {
+	rs io.ReadSeeker
+	br *bufio.Reader
+}
+
+func NewBufferedSeeker(rs io.ReadSeeker, size int) *BufferedSeeker {
+	return &BufferedSeeker{
+		rs: rs,
+		br: bufio.NewReaderSize(rs, size),
+	}
+}
+
+func (b *BufferedSeeker) Read(p []byte) (int, error) {
+	return b.br.Read(p)
+}
+
+func (b *BufferedSeeker) Seek(offset int64, whence int) (int64, error) {
+	if whence == io.SeekCurrent {
+		offset -= int64(b.br.Buffered())
+	}
+	n, err := b.rs.Seek(offset, whence)
+	if err != nil {
+		return 0, err
+	}
+	b.br.Reset(b.rs)
+	return n, nil
+}