Fix stale output when outputHeight changes from above stdout.rows to below stdout.rows

[thkim1011]

When the outputHeight goes from a value >= stdout.rows to a value < stdout.rows in between re-render, it is possible that the old content is not completely removed from the terminal.

This happens for three reasons

1. We actually want to consider the previous output height when deciding to entirely clear the terminal or only delete several lines. If the current output has a height >= stdout.rows, but we only need to clear the previous render's output, there's no point in writing ansiEscapes.clearTerminal. Similarly, if the current output has a height < stdout.rows but the previous output exceeded stdout.rows, then writing ansiEscapes.eraseLines(previousLineCount) won't clear all of the old output.
2. this.log.clear() doesn't actually track the height of the output if we rendered via the outputHeight >= this.options.stdout.rows conditional. I've added a helper LogUpdate.sync to keep it in sync.
3. The outputHeight >= this.options.stdout.rows conditional differs slightly in behavior to this.log in that it does not append a newline at the end.

Addressing all three of these points fixes the bug.

To test, I verified locally using a small example, and I've also added a test (see "erase screen where state changes in small viewport") which fails on master but passes in this branch.

Fixes #585

[thkim1011]

Unclear why this lint error just started to appear, but should be safe to ignore.

[thkim1011]

Correct me if I'm wrong but I think my PR fixes #585.

[thkim1011]

@sindresorhus can I get a re-run of the ci?

[thkim1011]

@sindresorhus just a heads up that this is ready for review.