Add missing metric provider documentations

[davidkopp]

There are currently 14 broken links in the READMEs of the metric providers in the GMT repository:

1. • https://docs.green-coding.io/docs/measuring/metric-providers/disk-io-cgroup-container/
2. • https://docs.green-coding.io/docs/measuring/metric-providers/cpu-utilization-mach-system/ → page is missing
3. • https://docs.green-coding.io/docs/measuring/metric-providers/gpu-energy-nvidia-smi-component/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/gpu-energy-nvidia-nvml-component/
4. • https://docs.green-coding.io/docs/measuring/metric-providers/disk-io-procfs-system/
5. • https://docs.green-coding.io/docs/measuring/metric-providers/cpu-utilization-cgroup-system-provider/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/cpu-utilization-cgroup-container-provider/ because the implementation is just a symlink
6. • https://docs.green-coding.io/docs/measuring/metric-providers/memory-used-procfs-system/ → page is missing
7. • https://docs.green-coding.io/docs/measuring/metric-providers/cpu-energy-rapl-msr-system/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/cpu-energy-rapl-msr-component/
8. • https://docs.green-coding.io/docs/measuring/metric-providers/network-connections-tcpdump-system/ → page is missing
9. • https://docs.green-coding.io/docs/measuring/metric-providers/psu-energy-ac-powerspy2/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/psu-energy-ac-powerspy2-machine/
10. • https://docs.green-coding.io/docs/measuring/metric-providers/network-proxy/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/network-connections-proxy-container/
11. • https://docs.green-coding.io/docs/measuring/metric-providers/disk-used-statvfs-system-provider/
12. • https://docs.green-coding.io/docs/measuring/metric-providers/psu-energy-sdia-system/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/psu-energy-sdia-machine/
13. • https://docs.green-coding.io/docs/measuring/metric-providers/memory-energy-rapl-msr-system/ → should be https://docs.green-coding.io/docs/measuring/metric-providers/memory-energy-rapl-msr-component/
14. • https://docs.green-coding.io/docs/measuring/metric-providers/network-io-procfs-system/ → page is missing

The links that are just wrong have to be fixed in the GMT repository.

EDIT 1: Pages of disk metric providers were added in #102

EDIT 2: Solved 5