`ZeroCopyBuf` was convenient to use, but sometimes it did hide details
that some copies were necessary in certain cases. Also it made it way to easy
for the caller to pass around and convert into different values. This commit
splits `ZeroCopyBuf` into `JsBuffer` (an array buffer coming from V8) and
`ToJsBuffer` (a Rust buffer that will be converted into a V8 array buffer).
As a result some magical conversions were removed (they were never used)
limiting the API surface and preparing for changes in #19534.
Uses SeqOneByteString optimization to do zero-copy `&str` arguments in
fast calls.
- [x] Depends on https://github.com/denoland/rusty_v8/pull/1129
- [x] Depends on
https://chromium-review.googlesource.com/c/v8/v8/+/4036884
- [x] Disable in async ops
- [x] Make it work with owned `String` with an extra alloc in fast path.
- [x] Support `Cow<'_, str>`. Owned for slow case, Borrowed for fast
case
```rust
#[op]
fn op_string_len(s: &str) -> u32 {
str.len() as u32
}
```
In the spec, a URL record has an associated "blob URL entry", which for
`blob:` URLs is populated during parsing to contain a reference to the
`Blob` object that backs that object URL. It is this blob URL entry that
the `fetch` API uses to resolve an object URL.
Therefore, since the `Request` constructor parses URL inputs, it will
have an associated blob URL entry which will be used when fetching, even
if the object URL has been revoked since the construction of the
`Request` object. (The `Request` constructor takes the URL as a string
and parses it, so the object URL must be live at the time it is called.)
This PR adds a new `blobFromObjectUrl` JS function (backed by a new
`op_blob_from_object_url` op) that, if the URL is a valid object URL,
returns a new `Blob` object whose parts are references to the same Rust
`BlobPart`s used by the original `Blob` object. It uses this function to
add a new `blobUrlEntry` field to inner requests, which will be `null`
or such a `Blob`, and then uses `Blob.prototype.stream()` as the
response's body. As a result of this, the `blob:` URL resolution from
`op_fetch` is now useless, and has been removed.
