Clarify Docker Setup for PMM Agent/Client #978

[catalinaadam]

To fix issue raised by community.
Could we instead use the steps from the new QuickInstall guide and replace the section?

[render]

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[render]

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[rnovikovP]

LGTM, but need an experts(internal) ✅

[BupycHuk]

pmm-agent requires 3 things to be persisted during restarts/recreations/upgrades, it's pmm-agent.yml, custom queries and temporary directory for vmagent buffer, so we need to mount volumes for them.
Second problem exist is trying to setup even if pmm-agent.yml exist and configured, I think we need to fix this problem. until that the recommendation to user PMM_AGENT_SETUP_FORCE=1 to not face error.
useful links:
https://www.notion.so/percona/How-to-run-pmm-client-as-a-side-container-e4f245a6594b43caa561e4ae2e2ad60a?pvs=4
https://perconacorp.slack.com/archives/C01NE1XPZBL/p1726738632233849?thread_ts=1726662402.677759&cid=C01NE1XPZBL