Allow iterable File constructor fileBits

[Copilot]

File constructor declarations only accepted BlobPart[], rejecting valid iterable inputs such as generators even though the platform API accepts iterable file bits.

• DOM declarations

  • Change File constructor fileBits to Iterable<BlobPart> in DOM and WebWorker libs.
  • Keep the DOM test fixture in sync.

• Regression coverage

  • Add a compiler test for generator-backed fileBits under es2022,dom.

new File((function* () {
    yield "a";
})(), "name");

• Fixes Change type of File constructor parameter fileBits to Iterable<BlobPart> #57520

[Jake Bailey (jakebailey)]

it's already not workable that we touch the generated files, but these are test fixtures that definitely should not be edited either