fix(k8smeta): introduce /proc scan to recover the pod uid of threads already spawned

[Andreagit97]

What type of PR is this?

/kind bug

/kind feature

Any specific area of the project related to this PR?

/area plugins

What this PR does / why we need it:

This PR introduces a proc-scan feature in the k8smeta plugin init phase. We need this to collect the pod uid of threads already running when Falco and the k8smeta plugin are started.

Which issue(s) this PR fixes:

Fixes #https://github.com/falcosecurity/plugins/issues/514

Special notes for your reviewer:

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[poiana]

LGTM label has been added.

Git tree hash: 7e40b508b8f3b049105fb9198e0119f088dba6c3

[alacuku]

Thanks for the fix @Andreagit97!

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[alacuku]

hey @Andreagit97, is this PR ready?

[Andreagit97]

yes! i removed the [WIP]

[poiana]

LGTM label has been added.

Git tree hash: dcd3c1e88753eab241d35ca59573f4d1a7de208a

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alacuku, Andreagit97, leogr

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/falcosecurity/plugins/blob/main/OWNERS)~~ [leogr] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment