Added perfetto support (CPU + Vulkan) backends

This uses perfetto in process profiling, and will produce a perfetto binary by
the end of the inference. This is very useful to help visualise how the
handles the inference.

Build:
cmake -S . -B build-vk -DCMAKE_BUILD_TYPE=RelWithDebInfo -DGGML_VULKAN=ON
cmake --build build-vk -j8

Run:
GGML_VK_PERF_SILENT=1 GGML_VK_PERF_LOGGER=1 LLAMA_PERFETTO_TRACE=./out.pftrace build-vk/bin/llama-cli -m model.gguf

Test:
Tested on M4 Mac

In detail this patch does the following:
1. Including the `LlamaPerfetto.h` header file, which contains the definitions for the Perfetto-related functions and variables used in this example.
2. Calling the `llama_perfetto_start()` function to start tracing at the beginning of the conversation.
3. Calling the `llama_perfetto_stop_flush()` function to stop tracing and flush the trace after each generation.
4. Adding a call to the `llama_perfetto_trace_begin_with_text()` function to begin an event in Perfetto with a text description of the current evaluation.
5. Adding a call to the `llama_perfetto_trace_end()` function to end the event after each evaluation.
6. Adding a call to the `llama_perfetto_counter_tokens_per_s()` function to update the Perfetto counter for tokens per second during idle periods.
7. Calling the `llama_perfetto_emit_gpu_timeline()` function to emit GPU timeline slices into Perfetto.
8. Adding a call to the `llama_perfetto_print_gpu_stats()` function to print GPU statistics at idle periods.
9. Calling the `llama_perfetto_flush_dump_stats()` function to flush and dump the Perfetto trace stats to a file at idle periods.

Author: walidbr