[whatwg/webidl] Fix `BufferSource` algorithms for shared and resizable buffers (PR #1529)

Previously, many `BufferSource` algorithms were using internal slots such as `[[ByteOffset]]` and `[[ByteLength]]` directly. However, with the addition of `SharedArrayBuffer` (#353, #1311) and `[AllowResizable]` (#982), this comes with extra caveats:
* To get the byte length of a `SharedArrayBuffer`, we need to use [`ArrayBufferByteLength`](https://tc39.es/ecma262/multipage/structured-data.html#sec-arraybufferbytelength) to match [`SharedArrayBuffer.prototype.byteLength`](https://tc39.es/ecma262/multipage/structured-data.html#sec-get-sharedarraybuffer.prototype.bytelength).
* To get the byte length of a ["length-tracking" typed array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray#behavior_when_viewing_a_resizable_buffer), we need to use [`TypedArrayByteLength`](https://tc39.es/ecma262/multipage/ordinary-and-exotic-objects-behaviours.html#sec-typedarraybytelength). Similarly, for a length-tracking `DataView`, we need to use [`GetViewByteLength`](https://tc39.es/ecma262/multipage/structured-data.html#sec-getviewbytelength).
* To get the byte offset of a typed array or `DataView`, we first need to check if the view is still inbounds using [`IsArrayBufferViewOutOfBounds`](https://tc39.es/ecma262/multipage/ordinary-and-exotic-objects-behaviours.html#sec-isarraybufferviewoutofbounds).

Transferring an `ArrayBuffer` must also take into account whether it should remain resizable or not. Fortunately, we can use the new [`ArrayBufferCopyAndDetach`](https://tc39.es/ecma262/multipage/structured-data.html#sec-arraybuffercopyanddetach) operation for that.
* I added an optional `preserveResizability` parameter to "transfer an `ArrayBuffer`", so specifications can choose whether to preserve resizability or not. By default, this is not preserved. (Most specs aren't using `[AllowResizable]` yet anyway.)
* I removed the `realm` parameter of that algorithm, since `ArrayBufferCopyAndDetach` doesn't accept such a parameter. [According to WebDex](https://dontcallmedom.github.io/webdex/t.html#transfer%40%40ArrayBuffer%40dfn), no specs were actually using that parameter anyway.

Open questions:
* [ ] When dealing with views backed by a `SharedArrayBuffer`, what memory ordering should we use? ECMAScript seems to use `SEQ-CST` pretty much everywhere (e.g. [`%TypedArray%.prototype.byteLength`](https://tc39.es/ecma262/multipage/indexed-collections.html#sec-get-%typedarray%.prototype.bytelength)), but ["get a copy of the bytes"](https://webidl.spec.whatwg.org/#dfn-get-buffer-source-copy) uses `UNORDERED` for `GetValueFromBuffer`.

Fixes #1312.
Fixes #1385.

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  https://github.com/whatwg/webidl/pull/1529

-- Commit Summary --

  * Fix buffer source's byte length
  * Add byte offset to ArrayBufferView
  * Fix writing bytes into an ArrayBufferView backed by a SharedArrayBuffer
  * Simplify writing into an ArrayBufferView
  * Move assert before conversion
  * Fix detached check
  * Use ArrayBufferCopyAndDetach to transfer an ArrayBuffer
  * Rework "get a copy of the bytes held"
  * Use IsArrayBufferViewOutOfBounds instead
  * Use SEQ-CST ordering to match ECMAScript

-- File Changes --

    M index.bs (85)

-- Patch Links --

https://github.com/whatwg/webidl/pull/1529.patch
https://github.com/whatwg/webidl/pull/1529.diff

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