update(engine): allow using -p to pass a format to plugin events

[LucaGuerra]

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind feature

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area engine

What this PR does / why we need it:

For Falco 0.38.1 we wish to fix a rule loader error when using -pk with k8s_audit plugin enabled. However, we may still wish to let people using plugins use -p to customize the output. So, following @sboschman 's suggestion we can enable -p for all sources and keep -pc, -pk etc for syscall sources.

Which issue(s) this PR fixes:

Fixes #3237

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

update(engine): enable -p option for all sources, -pk, -pc etc only for syscall sources

[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

[LucaGuerra]

@falcosecurity/falco-maintainers what do you think? Is it an acceptable compromise for 0.38.1?

[leogr]

I need to evaluate any possible edge cases, but it seems fine after a quick look. Thanks!

[incertum]

/approve

Nice!

[poiana]

LGTM label has been added.

Git tree hash: 89edfa2908bf63bb9b4098189d89d17cfd05e28c

[incertum]

/milestone 0.38.1

[LucaGuerra]

/unhold

[FedeDP]

/approve

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP, incertum, LucaGuerra

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