Support multiple kafka bootstrap servers

[ibice]

What type of PR is this?

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/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

Any specific area of the project related to this PR?

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/area build

/area config

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/area tests

What this PR does / why we need it:

• Support multiple Kafka bootstrap servers the same way other producers do. This way we can fetch initial cluster metadata from a different server in case one of them is down.
• Update the documentation to explicitly state that the kafka hostport property refers to bootstrap nodes and not just to brokers.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[poiana]

Welcome @ibice! It looks like this is your first PR to falcosecurity/falcosidekick 🎉

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ibice, Issif

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[poiana]

LGTM label has been added.

Git tree hash: 2eec98653a20b80b537d7e6a20badeb16d97af0d

[Issif]

Good to me, thanks