fs plugin support

[mkaufmaner]

Re: #2137

What does this PR do?
Remove fs plugin.

Motivation
This plugin was added a while ago with no clear use case. At best, it's unnecessary noise for most applications, and at worst, it causes issues like exposing errors that are later handled, general performance problems, etc. Removing this integration is the best course of action for now, and if there are clear use cases for it that users request afterwards, we can always bring it back but the result will likely be vastly different than the current approach since it should focus on the use case and not attempt to instrument every single function call including long-lived streams.

@rochdev A specific use case in which I have used the fs plugin is to identify dependencies which may be using the fs module. In my use case, we want to avoid writes to the file system as this can cause I/O problems within our container and degrade the overall performance of the application. Usually we have a good understanding of what these are but sometimes this is missed and aberrant behavior in select dependencies may utilize the filesystem. The dd-trace plugin was an easy way to identify these bottlenecks.

I am not asking to bring back support for the fs plugin, but maybe instead a way to warn when certain modules are being utilized.

[rochdev]

We are working on adding diagnostics channel events to Node core for module loading in nodejs/node#44340. With these events, it should be possible to know what dependencies are loaded, and what module loaded them. We'll be adding additional functionalities on top of these events in dd-trace as well.