llama: end-to-end tests (#19802)

* tests: add end-to-end tests per model architecture

* fixup for rebase

* fix use-after-free in llama-model-loader.cpp

* fix CI

* fix WebGPU

* fix CI

* disable CI for macOS-latest-cmake-arm64

* use expert_weights_scale only if != 0.0f

* comments

tools/results/README.md

@@ -0,0 +1,11 @@
+# Results
+
+The `llama-results` tool can be used to `--check` the outputs of a model vs. a previous commit to detect whether they have changed.
+Example usage:
+
+``` sh
+llama-results --model model.gguf --output results.gguf --prompt "People die when they are killed."  # writes results to file
+llama-results --model model.gguf --output results.gguf --prompt "People die when they are killed." --check  # compares results vs file
+```
+
+The metric by which the results are compared is the normalized mean squared error (NMSE) with a tolerance of $10^{-6}$.