Cleanup GPU and NPU utility code

[pjungkamp]

I've seen that you added NPU monitoring capabilities to Resources and wanted to check out the code. I also looked into PR #431.

I think that the code becomes "simpler" by using dynamic dispatch using Deref on the Gpu and Npu types. This required me to make the GpuImpl and NpuImpl traits object-safe and I had to move the generic read_sysfs_int/read_sysfs_file/read_device_int/read_hwmon_int functions out of the GpuImpl and NpuImpl traits. I consolidated these in a new read_sysfs function in src/utils/mod.rs.

I also refactored some code to cut down on some of the PathBuf and String allocations where not necessary.

While building the code using flatpak-builder I ran into timeouts on dmidecode. I've changed the download URL from the git.savannah.nongnu.org/cgit endpoint to download-mirror.savannah.gnu.org, which should be much faster.

[pjungkamp]

You would need to shuffle some things #431 but at least you won't have to worry about all the match statements in utils/npu/mod.rs anymore, those were all consolidated in the Deref implementation.

[nokyan]

Thank you so much! When writing this code, I tried to figure that out but failed, so thanks a lot for fixing it up! :)
I will test it later today or tomorrow.

[nokyan]

Just tested it, works as intended and is really nice code! Thanks again!

[pjungkamp]

Awesome! I thought about opening an issue describing the cleanups I imagined, started writing some text, got bored, and wrote the code instead. If you want some code reviews just tag me! 😄

Grüße aus dem Münsterland!