Set default (cluster-)agent version to `7.54.0`

[L3n41c]

What this PR does / why we need it:

Set default agent and cluster-agent version to 7.54.0.

Which issue this PR fixes

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [X] Chart Version bumped
• [X] Documentation has been updated with helm-docs (run: .github/helm-docs.sh)
• [X] CHANGELOG.md has been updated
• [X] Variables are documented in the README.md
• [] For Datadog Operator chart or value changes update the test baselines (run: make update-test-baselines)

[L3n41c]

/merge

[dd-devflow[bot]]

:steam_locomotive: MergeQueue: pull request added to the queue

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Use /merge -c to cancel this operation!