Runner for Ollama engine

This provides integration with the new Ollama engine
(5824541 next ollama runner (#7913)) and the rest of the Ollama
infrastructure such as the runner and Ollama server.

In addition, it also builds out the KV cache infrastructure to
support requirements of how Ollama runs models such as:
 - Parallel processing
 - Memory management for defragmentation and shifting
 - Multi-modal modals

Both old and new engines continue to be supported. By default, only
the old engine is used. To enable the new engine:

Start the server with the OLLAMA_NEW_ENGINE environment variable set:
OLLAMA_NEW_ENGINE=1 ./ollama serve

Start a model that is supported by the Ollama engine. This one is Llama 3.1 8b Q4_K_M:
./ollama run jessegross/llama3.1

model/model_test.go

@@ -78,7 +78,7 @@ func TestPopulateFields(t *testing.T) {
 
 	var m fakeModel
 	v := reflect.ValueOf(&m)
-	v.Elem().Set(populateFields(&fakeBackend{
+	v.Elem().Set(populateFields(Base{b: &fakeBackend{
 		names: []string{
 			"input.weight",
 			"blk.0.attn_q.weight",
@@ -90,7 +90,7 @@ func TestPopulateFields(t *testing.T) {
 			"output_norm.weight",
 			"output.weight",
 		},
-	}, v.Elem()))
+	}}, v.Elem()))
 
 	if diff := cmp.Diff(fakeModel{
 		Input:      &nn.Embedding{Weight: &fakeTensor{Name: "input.weight"}},
@@ -121,11 +121,11 @@ func TestPopulateFieldsAlternateName(t *testing.T) {
 
 	m := fakeModel{}
 	v := reflect.ValueOf(&m)
-	v.Elem().Set(populateFields(&fakeBackend{
+	v.Elem().Set(populateFields(Base{b: &fakeBackend{
 		names: []string{
 			"input.weight",
 		},
-	}, v.Elem()))
+	}}, v.Elem()))
 
 	if diff := cmp.Diff(fakeModel{
 		Input:  &nn.Embedding{Weight: &fakeTensor{Name: "input.weight"}},