Properly set the errored property for --report options

[nex3]

This sets the errored property (and thus the exit code) as long as
any warning has severity "error", which includes warnings generated by
--report options.

Closes #5046

[hudochenkov]

Do you think it is possible to add a test for this?

We have tests for different exit codes in https://github.com/stylelint/stylelint/blob/master/lib/__tests__/cli.test.js.

[nex3]

There are already tests in there that verify the exit codes for report flags:

stylelint/lib/__tests__/cli.test.js

Lines 242 to 255 in bf6a881

	it('reports disallowed disables', async () => {
	await cli([
	'--config',
	replaceBackslashes(path.join(fixturesPath, 'config-block-no-empty-report-disables.json')),
	replaceBackslashes(path.join(fixturesPath, 'empty-block-with-relevant-disable.css')),
	]);
	expect(process.exitCode).toBe(2);
	expect(process.stdout.write).toHaveBeenCalledTimes(1);
	expect(process.stdout.write).toHaveBeenCalledWith(
	expect.stringContaining('Rule "block-no-empty" may not be disabled'),
	);
	});

It's not clear to me why that wasn't failing prior to this PR, or how to write a test that wouldn't just recapitulate what that test is already doing.

[vankop]

@nex3 @hudochenkov please rereview

[nex3]

Tests look good to me, just need @vankop to approve the PR and I can land it.