filebeat/input/tcp: add support for TCP input metrics

[efd6]

What does this PR do?

This adds metrics for TCP packet count and total bytes, and histograms for time required to process TCP packets prior to acking from a publication and time between TCP packet arrivals.

Why is it important?

This allows us to help users configure their systems to match the requirements that they have.

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.

Author's Checklist

• [ ]

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[elasticmachine]

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• Start Time: 2023-01-23T02:06:21.982+0000

• Duration: 73 min 44 sec

Test stats 🧪

Test	Results
Failed	0
Passed	7204
Skipped	742
Total	7946

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[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[andrewkroh]

LGTM