sync: release 0.39.x

[FedeDP]

What type of PR is this?

/kind cleanup

Any specific area of the project related to this PR?

What this PR does / why we need it:

Syncs 0.39.x release branch with latest master fixes, by cherrypicking:

• update(systemd): add falco.service alias to all systemd units #3332
• fix(userspace/falco): properly account for plugin with CAP_PARSING when computing interesting sc set #3334
• fix(falco): allow plugin init_config map in json schema #3335
• fix(falco_metrics): fix prometheus metrics to be compliant with best practices #3337
• fix(engine): sync outputs before printing stats at shutdown #3338

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[FedeDP]

/milestone 0.39.x

[poiana]

@FedeDP: The provided milestone is not valid for this repository. Milestones in this repository: [0.39.0, 0.40.0, 1.0.0, TBD]

Use /milestone clear to clear the milestone.

In response to this:

/milestone 0.39.x

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[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP

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[github-actions]

This PR may bring feature or behavior changes in the Falco engine and may require the engine version to be bumped.

Please double check userspace/engine/falco_engine_version.h file. See versioning for FALCO_ENGINE_VERSION.

/hold

[FedeDP]

/unhold

[LucaGuerra]

/milestone 0.39.0