fix(ext/fetch): implement missing Request properties (#34607)
## Summary
`Request` was missing properties that the [Fetch
standard](https://fetch.spec.whatwg.org/#request-class) (and our own
type declarations in `lib.deno_fetch.d.ts`) require. They returned
`undefined`, diverging from Node.js and browsers.
This PR adds the missing properties along with the corresponding
`RequestInit` fields and WebIDL enum converters:
- `cache` / `RequestCache`
- `credentials` / `RequestCredentials`
- `integrity`
- `keepalive`
- `mode` / `RequestMode`
- `referrer`
- `referrerPolicy` / `ReferrerPolicy`
Defaults match the Fetch standard for a `new Request(string)`:
| Property | Default |
| --------------- | ---------------- |
| cache | `"default"` |
| credentials | `"same-origin"` |
| integrity | `""` |
| keepalive | `false` |
| mode | `"cors"` |
| referrer | `"about:client"` |
| referrerPolicy | `""` |
Inheritance behavior: when constructing or cloning from another
`Request`, all of these inherit from the source request. Spec invariants
are enforced — `mode: "navigate"` and `cache: "only-if-cached"` outside
of `same-origin` mode both throw `TypeError`. The `referrer` getter
serializes the internal `"client"`/`"no-referrer"` sentinels to
`"about:client"` and `""` per spec.
Fixes #27763.
Closes denoland/orchid#352
## Test plan
- [x] `cargo build --bin deno`
- [x] Added unit tests covering defaults, init reflection, inheritance
from another Request, cloning, mode/cache invariants, and the special
referrer values
- [x] `deno test tests/unit/request_test.ts` (run against the new
binary)
- [x] `deno fmt --check` on touched files
- [x] `deno lint` on touched files
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Co-authored-by: divybot <divybot@users.noreply.github.com>
Co-authored-by: Divy Srivastava <me@littledivy.com>
