[Console]Improve formatter for double-width character

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | yes for one that expecting current broken output
| Deprecations? | not
| Tests pass?   | yes
| License       | MIT

As mb_strlen just returns "how many chars in the string",
formatting with double-width character is bit broken.

The test I add is skipped when mbstring extension is not loaded.
I'm afraid if some of you cannot properly display japanese string.
(表示するテキスト just means "Some text to display")