[8.15](backport #40081) [debugPrintProcessor]: exit directly when log doesn't have debug level enabled

[mergify]

Proposed commit message

This PR is the aftermath of profiling the netflow integration test of this PR (PS: the pcap I used as input is ~25MB thus I won't include it in beats repo)

So this is the cpu profile flamegraph before the commit of this PR

As we can see debugPrintProcessor is invoked and we pay the "performance" price of encoding every event in json even when our log isn't set up with DEBUG level.

The respective cpu profile flamegraph after this PR with debugPrintProcessor still being there but exiting directly when log DEBUG is not enabled

Extracting the average EPS of the aformentioned netflow integration tested on my local macbook with a local ES inside a container

Before this PR	With this PR
18490	33760

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

N/A

Author's Checklist

N/A

How to test this PR locally

Help get this PR merged or clone it and apply this small commit there 🙂

cd x-pack/filebeat
mage docker:composeUp

run go profiler against TestNetFlowIntegration

Related issues

• Relates [Filebeat] Auto-scale number of netflow decoder workers  #37761

Use cases

N/A

Screenshots

Look at description

Logs

N/A

---

This is an automatic backport of pull request #40081 done by Mergify.

[botelastic]

This pull request doesn't have a Team:<team> label.