Fix thread safety issue in async fs functions file paths

[Jarred-Sumner]

What does this PR do?

Call .isolatedCopy() on strings we pass from JS -> another thread so that atomic strings doesn't crash. Fixes a crash impacting Astro CLI & Vite.

How did you verify your code works?

Added a couple automated tests. Manually checked memory usage difference

[github-actions]

❌ @Jarred-Sumner 1 files with test failures on bun-darwin-aarch64:

• test/js/bun/test/test-test.test.ts

View test output

^{#298d63b2d4c36591d93c320ea1d6b701416dd789}

[github-actions]

❌ @Jarred-Sumner 1 files with test failures on linux-x64:

• test/js/third_party/prisma/prisma.test.ts

View test output

^{#298d63b2d4c36591d93c320ea1d6b701416dd789}

[github-actions]

❌ @Jarred-Sumner 1 files with test failures on linux-x64-baseline:

• test/js/third_party/prisma/prisma.test.ts

View test output

^{#298d63b2d4c36591d93c320ea1d6b701416dd789}

[github-actions]

❌ @Jarred-Sumner 4 files with test failures on bun-darwin-x64-baseline:

• test/js/bun/spawn/spawn-streaming-stdin.test.ts
• test/js/bun/sqlite/sqlite.test.js
• test/js/third_party/webpack/webpack.test.ts
• test/js/web/timers/setTimeout.test.js

View test output

^{#298d63b2d4c36591d93c320ea1d6b701416dd789}