[Performance] Memoize shouldDisplayColors

[gonzaloriestra]

WHY are these changes introduced?

High-frequency logging paths call shouldDisplayColors repeatedly to determine if output should be colorized. Accessing process.env and checking TTY status on process.stdout involves small but measurable overhead that adds up over the lifecycle of a CLI command, especially when debug logging is enabled or many messages are processed.

WHAT is this pull request doing?

This PR introduces memoization for the shouldDisplayColors function in @shopify/cli-kit.

• Results are cached in a module-level variable when called with the default process object.
• Custom process objects (e.g., used in unit tests) bypass the cache to ensure isolation and correct behavior during testing.
• The logic remains identical, preserving current behavior while improving efficiency for the common case.

How to test your changes?

CI

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

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PR created automatically by Jules for task 303941856508991664 started by @gonzaloriestra

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[ryancbahan]

Do we know what the actual overhead is here? i'm a little wary of unmeasured optimizations.