Add logging section for agent k8s standalone containers

[michel-laterman]

Summary

Add a section to explain needed changes in order to log to a user defined path when running the agent in a standalone k8s container.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

[github-actions]

Vale Linting Results

Summary: 3 suggestions found

💡 Suggestions (3)

File	Line	Rule	Message
reference/fleet/running-on-kubernetes-standalone.md	269	Elastic.Capitalization	'Logging Considerations' should use sentence-style capitalization.
reference/fleet/running-on-kubernetes-standalone.md	271	Elastic.FutureTense	'will log' might be in future tense. Write in the present tense to describe the state of the product as it is now.
reference/fleet/running-on-kubernetes-standalone.md	273	Elastic.Wordiness	Consider using 'to' instead of 'In order to'.

[github-actions]

🔍 Preview links for changed docs

• reference/fleet/running-on-kubernetes-standalone.md