pipeline: inputs: create gpu-metrics docs. Fixes #2080

[Xata]

Hello! I saw that there was no documentation for the new GPU metrics plugin. My system fits the current requirements for the plugin to work, so I went ahead and documented the feature.

My system specs are:

• CPU: Ryzen 7 9700X with Radeon Graphics
• GPU: AMD Radeon RX 7900 GRE
• Operating System: EndeavourOS
• Kernel: 6.17.4-arch2-1
• Architecture: x86_64

I did have to build Fluent Bit for my system but it did compile just fine on EndeavourOS. These are the configuration files that I made for testing:

test-gpu.yaml:

pipeline:
   inputs:
      - name: gpu_metrics
        scrape_interval: 2
        path_sysfs: /sys
        cards_include: "1"
        cards_exclude: "0"
        enable_power: true
        enable_temperature: true

   outputs:
      - name: stdout
        match: '*'

test-gpu.conf:

[INPUT]
   Name                gpu_metrics
   scrape_interval     2
   path_sysfs          /sys
   cards_include       1
   cards_exclude       0
   enable_power        true
   enable_temperature  true

[OUTPUT]
   Name   stdout
   Match  *

After compiling Fluent Bit I ran these commands to test:

./build/bin/fluent-bit -c test-gpu.yaml
./build/bin/fluent-bit -c test-gpu.conf

I followed the CPU metrics and the memory metrics documentation when writing this. I have not tested this on other operating systems. As per the code, I've explicitly mentioned that only AMD GPUs are supported right now.

Please let me know if there are any edits that I need to make!

[Xata]

I'm working on trying to fix the vale errors in my documentation.

Edit:
I've modified some of the documentation. However, it looks like Vale is popping errors about:

suggestion  Spelling check: 'GPUs'?         FluentBit.Spelling
suggestion  'Multiple GPU systems'          FluentBit.Headings 
                     should use sentence-style                          
                     capitalization.
suggestion  'GPU detection' should use      FluentBit.Headings 
                     sentence-style capitalization.
suggestion  Spelling check:                 FluentBit.Spelling 
                     'cards_include'?
suggestion  Spelling check: 'sysfs'?        FluentBit.Spelling
suggestion  Spell out 'RPM', if it's        FluentBit.Acronyms 
                     unfamiliar to the audience.
suggestion  Spell out 'PWM', if it's        FluentBit.Acronyms 
                     unfamiliar to the audience.
suggestion  Spelling check:                 FluentBit.Spelling 
                     'enable_power'?                                    
suggestion  Spelling check:                 FluentBit.Spelling 
                     'enable_temperature'?
suggestion  Spelling check: 'gpu_metrics'?  FluentBit.Spelling

Is it safe to ignore some of those or should that be correct?