Integrate perflib

[jkroepke]

Fixes #1240

What I do here:

1. Copy /~https://github.com/leoluk/perflib_exporter/tree/master/perflib to /perflib
2. Copy needed consts from /~https://github.com/leoluk/perflib_exporter/blob/master/collector/mapper.go into /perflib/consts.go
3. Remove unused helper
4. Remove HelpName lookups, since windows_exporter do not use them
5. Introduce lazy-loading for QueryNameTable to reduce startup times.
6. Remove the additional loop at the QueryNameTable initialization.

[jkroepke]

Implementations since from point of view, we may need some additional tests.

[jkroepke]

I run some test on Windows Server, I go no issues with default settings.

[breed808]

Looking at the commits the feature branch could do with a rebase (we're currently proposing to merge a merge commit); I have no objections to the change itself, it's looking good.

Once rebased, are you happy for me to merge this?

[jkroepke]

Once rebased, are you happy for me to merge this?

Let me take an other test, in case I do the rebase incorrectly.

[jkroepke]

Everything seems working fine in default configuration.

[leoluk]

Are you interested in taking over perflib library maintenance? I no longer operate any Windows server and I'd be more than happy to archive the repo and point users here instead.

[jkroepke]

@leoluk this PR contains only a subset of perflib_exporter. Only the functions and vars that windows_exporter requires are part of this PR

I guess to maintain the perflib_exporter, it requires an more deeper knowledge about the WMI metrics itself which I do not have.

[breed808]

@jkroepke are you happy for this to be merged? I have no further concerns or queries for this change.

[jkroepke]

I'm happy, yes