* vulkan: fix GPU deduplication logic.
As reported in https://github.com/ggml-org/llama.cpp/issues/19221, the
(same uuid, same driver) logic is problematic for windows+intel igpu.
Let's just avoid filtering for MoltenVK which is apple-specific, and
keep the logic the same as before 88d23ad5 - just dedup based on UUID.
Verified that MacOS + 4xVega still reports 4 GPUs with this version.
* vulkan: only skip dedup when both drivers are moltenVk
Deduplication here relied on the fact that vulkan would return unique
UUID for different physical GPUs. It is at the moment not always the case.
On Mac Pro 2019 running Mac OS, with 2 Vega II Duo cards (so, 4 GPU total),
MotlenVK would assign same UUID to pairs of GPUs, unless they
are connected with Infinity Fabric.
See more details here: KhronosGroup/MoltenVK#2683.
The right way is to fix that in MoltenVK, but until it is fixed,
llama.cpp would only recognize 2 of 4 GPUs in such configuration.
The deduplication logic here is changed to only filter GPUs if UUID is
same but driver is different.
Add tracking for high watermark cache usage and make it available in /metrics endpoint.
Use-case: Tracking largest needed cache usage under realistic workload
to better understand memory requirements and be able to adjust
cache size/quantization for model/cache accordingly.
There was a typo-like error, which would print the same number twice if
request is received with n_predict > server-side config.
Before the fix:
```
slot launch_slot_: id 0 | task 0 | n_predict = 4096 exceeds server configuration, setting to 4096
```
After the fix:
```
slot launch_slot_: id 0 | task 0 | n_predict = 8192 exceeds server configuration, setting to 4096
```
