chore(prebuild-config, config-plugins): rewrite tests to use latest template for fixtures (#21339)

# Why

- The previous tests were using static representations of the versioned
fixtures. This me

chore(prebuild-config, config-plugins): rewrite tests to use latest template for fixtures (#21339)

# Why

- The previous tests were using static representations of the versioned
fixtures. This meant that many tests were possibly outdated.
- Now that the CLI is versioned, we can test against the latest
templates to ensure our config plugins are always up to date.

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# How

- Pull in fixtures from the local template.
- Rewrite tests to work with new fixtures.

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# Test Plan

- Tests should continue to pass.

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Co-authored-by: Expo Bot <[email protected]>

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