Add network docs

[oruebel]

Fix #24

• Add documentation about the network tracking and how to use it in the benchmarks
• Update the NetworkTracker class to track the total time directly, rather than having the network_activity_tracker track the time separately. This change addresses the following issues: a) NetworkTracker was missing the total time so results are not the same compared to network_activity_tracker and 2) NetworkTracker.asv_network_statistics was not being updated in the network_activity_tracker so the timing result was not being recorded.
• Update NetworkTracker and network_activity_tracker to allow the user to optionally set the process ID to track. This will be useful if/when we need to run code we want to profile in a separate process (e.g., when running in node.js)

[CodyCBakerPhD]

Suggested change

Functions that require network access ---such as reading a file from S3--- are often a black box, with functions in other libraries (e.g., `h5py`, `fsspec` etc.) managing the access to the remote resources. The runtime performance of such functions is often inherently driven by how these functions utilize the network to access the resources. It is, hence, important that we can profile the network traffic that is being generated to better understand, e.g., the amount of data that is being downloaded and uploaded, the number of requests that are being sent/received, and others.

Functions that require network access ---such as reading a file from S3--- are often a black box, with functions in other libraries (e.g., `h5py`, `fsspec` etc.) managing the access to the remote resources. The runtime performance of such functions is often inherently driven by how these functions utilize the network to access the resources. It is, hence, important that we can profile the network traffic that is being generated to better understand the amount of data that is being downloaded and uploaded, the number of requests that are being sent/received, and so on.

[CodyCBakerPhD]

Some minor style suggestions based on rendering on https://nwb-benchmarks--35.org.readthedocs.build/en/35/writing_benchmarks.html#network-tracking-benchmarks

As a reminder, should you choose to accept the suggestions, you can batch them from the 'files changes' view on GitHub by selecting 'add suggestion to batch' and then 'commit X suggestions' to result in only a single commit; or if you prefer to stand by original style, just go ahead and merge