Terminal.scroll should be moved into BufferService

[Tyriar]

See

xterm.js/src/browser/Terminal.test.ts

Lines 1421 to 1430 in 45077d7

	describe('Terminal InputHandler integration', () => {
	function getLines(term: TestTerminal, limit: number = term.rows): string[] {
	const res: string[] = [];
	for (let i = 0; i < limit; ++i) {
	res.push(term.buffer.lines.get(i)!.translateToString(true));
	}
	return res;
	}
	// This suite cannot live in InputHandler unless Terminal.scroll moved into IBufferService

, #2724 (review)