Input memory exhaustion

[Tyriar]

Forked off from #2077

The time-based input limiting contains a buffer, that gets drained only once all chunks were handled.
This way fast producers can easily exhaust memory and will crash the terminal / browser engine.

Partial fix: Trim/slice already handled chunks from the buffer.

xterm.js/src/Terminal.ts

Lines 1441 to 1447 in af81acc

	if (this.writeBuffer.length > bufferOffset) {
	// Allow renderer to catch up before processing the next batch
	setTimeout(() => this._innerWrite(bufferOffset), 0);
	} else {
	this._writeInProgress = false;
	this.writeBuffer = [];
	}

[Tyriar]

Trimming writeBuffer once bufferOffset reaches some threshold should be enough to fix this.