metrics: add pprof support

[Fricounet]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Create new function RegisterPprofToServer to enable pprof profiling on the existing metrics server. This can be used to gain useful insights on the performance of the application.

Which issue(s) this PR fixes:

Fixes #137

Special notes for your reviewer: I tested the modified lib buy building locally one of the CSI sidecars and deploying it to a test cluster. I was able to access the pprof endpoints with a curl form inside the container.

Does this PR introduce a user-facing change?:

Added RegisterPprofToServer function to enable pprof on metrics server

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: Fricounet / name: Baptiste Girard-Carrabin (21b97c0d3bd4440131c675a832901f4be3ad57f5)

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[k8s-ci-robot]

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[xing-yang]

/ok-to-test

[xing-yang]

/assign @jsafrane

[jsafrane]

/lgtm /approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Fricounet, jsafrane

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubernetes-csi/csi-lib-utils/blob/master/OWNERS)~~ [jsafrane] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment