Debugfs collector

[thiagoftsm]

Summary

Fixes #15001
Fixes #14927

Test Plan

1. Mount debugfs if it nos mounted:

# mount -t debugfs nodev /sys/kernel/debug

2. Enable zswap:

# echo 1 > /sys/module/zswap/parameters/enabled

3. Compile branch and check metrics. You can compare values on dashboard with file values running:

# find /sys/kernel/debug/zswap/ -type f -exec grep -H . {} \;
# cat /sys/kernel/debug/extfrag/extfrag_index

Additional Information

As we define in our meeting today, the PR with alerts will be a separated PR, because I had to address 19 files in this PR.

For users: How does this change affect me?

Describe the PR affects users: - Which area of Netdata is affected by the change? plugins - Can they see the change or is it an under the hood? If they can see it, where? Yes, after to be merged users will be another plugin running when `debugfs` is mounted. - How is the user impacted by the change? More information about memory - What are there any benefits of the change? We will have more metrics helping to understand better memory on host.

[Ferroin]

This will also need handling in our packaging code, and the static builds, but I can take care of that shortly before we merge it if desired (I’m hesitant to do any of it any sooner as we have a lot of things changing in those areas in the very near future).

[thiagoftsm]

Thank you @Ferroin !
In this first stage I only modified autoconf to have conditions to develop, as soon collector is ready, I will ping you. 🤝

[Ancairon]

Slight docs change, the rest lgtm

[Ferroin]

Two suggested changes, but otherwise LGTM.