WIP: llama: Vulkan: Fix Adreno Q8_0 issues.

[infinitalo]

This MR is a work-in-progress.

The current commits are able to get inference working for Q8_0 on Adreno 830 (Samsung S25), but finetuning still crashes.

We're currently working on a fix for lora-finetuning on Adreno A830, but you can use this for testing in the meanwhile.

[infinitalo]

Steps to run the backend-ops test suite:

1. Set up your Android environment for testing llama.cpp. You can use this comment as a reference if you haven't built it already: Add initial LoRA finetuning support; vulkan OUT_PROD; vulkan cross-entropy-backward #5 (comment)
2. Configure your build with: cmake -B build -DGGML_VULKAN=1 -DCMAKE_BUILD_TYPE=Debug -DBUILD_TESTING=ON
3. Build llama.cpp: cmake --build build --config Debug -j2
4. Run the backend-ops tests: ./build/bin/test-backend-ops
5. You can also run tests for specific operators with the -o option, for example: ./build/bin/test-backend-ops -o MUL_MAT

This PR has a commit disabling several tests for quantized datatypes that are not currently working properly on Adreno 830.

If you run the test suite as described above with this branch, it should say 2/2 backends passing at the end, with no failing tests on A830, as the attached file shows.

test_adreno_q8_inf2.txt