llama : Add FP8 KV-cache support (#28392)
* Add FP8 KV-cache support
* Add tests for scaled, FP8 KV-cache to test-backend-ops
* Fix get_*_scale mapping and dequnatize FP8 also before rope shift
* Normalizes cache-scale names independently of projection layout.
While fused KQV is currently impractival for non-shared scales, this is
an improvement for future use regardless
* Enable Gemma 4 Assistant with FP8 by storing and fetching scale ptrs
* Update comment wording
* Move E2E FP8 KV cache tests to test-llama-archs
They belong there as they are not just a test for ggml's backend ops
* Increase support surface, remove seed
* make scaled kv generic
* Fix CI failings for test-kv-cache
https://github.com/ggml-org/llama.cpp/actions/runs/38718763447/job/116367842578?pr=28392
* CI: execute kv-cache-scale tests
* exclude fp8-kv tests from OpenVINO
* Fix linting errors of test_kv_cache_scales
* Disable kv-ffload=false + multi-GPU tests for FP8
See https://github.com/ggml-org/llama.cpp/actions/runs/38952722084/job/117148353699?pr=28413
* Adjust test label for test-kv-cache.cpp
* Fix conflict-resolution mistakes in test-kv-cache.cpp
https://github.com/ggml-org/llama.cpp/actions/runs/40554674463/job/122367426461?pr=28392
* Move KV tests to test-fp8.cpp
https://github.com/ggml-org/llama.cpp/pull/27512#discussion_r4410518158
* Remove tmp file for test-kv-cache-scales.py on Windows as well
* Fix fp8 kv cache test by population kv_source_impl
* Exclude models that consume KV cache directly
* Remove obsolete comment
* Allow BF16 scales as well for KV cache
* Rename *_cache_scale to *_cache_s
https://github.com/ggml-org/llama.cpp/pull/28392#discussion_r4517194999
* Move `is_type_scaled()` to `llama-kv-cache.cpp`
