Align tmp/run volume names and remove system-probe DogStatsD mount

[tbavelier]

What does this PR do?

Aligns Operator-generated Datadog pod volume names and mounts with the Helm chart by:

• renaming the shared /tmp volume from tmp to tmpdir
• renaming the shared Agent run directory volume from pointerdir to datadogrun
• reusing the shared Agent run directory constants in log collection when it replaces the default emptyDir with the configured pointer hostPath
• renaming log collection container log volumes from logcontainerpath to logdockercontainerpath and from symlinkcontainerpath to logscontainerspath
• removing the DogStatsD socket volume mount from the system-probe container
• updating the Cluster Agent default pod spec expectations for the renamed /tmp volume

Motivation

Match Helm chart volume naming and GKE Autopilot allowlist expectations while keeping the existing Agent run directory behavior. Log collection still replaces the default Agent run directory volume source with the configured hostPath for log pointer state, but now uses the same datadogrun volume name as the default pod template.

Additional Notes

This PR does not remove the /opt/datadog-agent/run mount from system-probe; it only removes the unnecessary DogStatsD socket mount from that container.

Minimum Agent Versions

No minimum version changes.

• Agent: N/A
• Cluster Agent: N/A

Describe your test plan

go test ./internal/controller/datadogagent/component/agent ./internal/controller/datadogagent/feature/logcollection ./internal/controller/datadogagent/feature/cws ./internal/controller/datadogagent/feature/dogstatsd
go test ./internal/controller/datadogagent -run Test
go test ./internal/controller/datadogagent/feature/logcollection
go test ./internal/controller/datadogagent/component/agent

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label
• All commits are signed

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.76%. Comparing base (d3652e6) to head (d781025).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2985   +/-   ##
=======================================
  Coverage   40.75%   40.76%           
=======================================
  Files         332      332           
  Lines       28197    28196    -1     
=======================================
  Hits        11493    11493           
+ Misses      15929    15928    -1     
  Partials      775      775           

Flag	Coverage Δ
unittests	40.76% <ø> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
...controller/datadogagent/component/agent/default.go	44.13% <ø> (+0.06%)	⬆️
...ller/datadogagent/feature/logcollection/feature.go	84.14% <ø> (ø)

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[datadog-datadog-prod-us1]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 41.07% (+0.00%)

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