refactor(cli/init): deduplicate asset creation logic

[DonIsaac]

What does this PR do?

Centralizes asset creation logic for bun init.

How did you verify your code works?

I wrote automated tests

[robobun]

^{Updated 6:06 PM PT - Jan 10th, 2025}

❌ @DonIsaac, your commit e0f08ac has 1 failures in #9395:

• test/bundler/bundler_compile.test.ts - annotation error on 🐧 3.20 aarch64

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🧪   try this PR locally:

bunx bun-pr 16294

[DonIsaac]

• test(cli/init): refactor init.test.ts #16297
• feat(cli/init): new repos use text-based lockfile #16295
• refactor(cli/init): deduplicate asset creation logic #16294 👈 (View in Graphite)
• main

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[DonIsaac]

Builds are failing because Graphite's default branch name causes folder names to be too long on windows. I'll make another PR fixing this.