fix(mock-doc): add File and Blob constructors

[xonaib]

Fixes #3539

What changed

• Adds mock Blob and File constructors to Stencil's mock DOM globals.
• Exports the constructors from @stencil/core/mock-doc.
• Adds focused coverage for Blob and File in the global mock-doc tests.

Verification

• npm run tsc.prod
• node --experimental-vm-modules .\node_modules\jest\bin\jest.js src/mock-doc/test/global.spec.ts --runInBand
• npx eslint src/mock-doc/blob.ts src/mock-doc/file.ts src/mock-doc/global.ts src/mock-doc/index.ts src/mock-doc/test/global.spec.ts