Boost: Align responses from Cloud to sizes within plugin

[LiamSarsfield]

Note

Merge this PR after #43225 is merged.

Proposed changes:

• Moves the much of the Optimization code from the main LCP class to a new one LCP_Optimizer.
• Aligns the response/LCP Storage data we receive from the Cloud with existing Boost implementation.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Ensure that the branch from the Boost Cloud is checked out locally: https://github.com/Automattic/boost-cloud/pull/680

[github-actions]

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[jp-launch-control]

Code Coverage Summary

No summary data is available for parent commit b350545, so cannot calculate coverage changes. 😴

If that commit is a feature branch rather than a trunk commit, this is expected. Otherwise, this should be updated once coverage for b350545 is available.

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