Buffer.prototype.asciiSlice, etc use offset, length instead of start, end

[mhart]

The following is fine in Node.js:

> Buffer.from('abcd').utf8Slice(2, 3).toString()
'c'

But in workerd it throws:

The value of "length" is out of range. It must be >= 0 && <= 2. Received 3

Relevant source for us:

workerd/src/node/internal/internal_buffer.ts

Lines 758 to 799 in 7aa2d5f

	Buffer.prototype.asciiSlice = function asciiSlice(offset: number, length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, ASCII);
	};
	Buffer.prototype.base64Slice = function base64Slice(offset: number, length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, BASE64);
	};
	Buffer.prototype.base64urlSlice = function base64urlSlice(offset: number, length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, BASE64URL);
	};
	Buffer.prototype.hexSlice = function hexSlice(offset: number, length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, HEX);
	};
	Buffer.prototype.latin1Slice = function latin1Slice(offset: number,
	length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, LATIN1);
	};
	Buffer.prototype.ucs2Slice = function ucs2Slice(offset: number, length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, UTF16LE);
	};
	Buffer.prototype.utf8Slice = function utf8Slice(offset: number, length: number) {
	validateOffset(offset, "offset", 0, this.length);
	validateOffset(length, "length", 0, this.length - offset);
	return bufferUtil.toString(this, offset, offset + length, UTF8);
	};

Relevant source for Node.js:

https://github.com/nodejs/node/blob/8d3758487498e3c1edfd0f6f4d36d0fb3a3fab4e/src/node_buffer.cc#L545-L551

(Note also that Node.js allows end < start so long as both are not out of bounds and sets:if (end < start) end = start)