Xlsx Column Autosize Approximate for CJK

[oleibman]

Fix #3405. Autosize is definitely not working well with CJK characters (column is not wide enough). User reports a workaround using mb_strwidth to calculate and set the column width. PhpSpreadsheet uses mb_strlen for width calculations. Change it to use mb_strwidth instead. For non-CJK strings, the results will be identical (and there are already unit tests on such strings which assert the expected results, and these tests did not need to change). For CJK strings, the results will be wider. The string I'm using to test comes from the issue. It currently results in a column width of 30.564. When I open the resulting sheet in Excel and auto-fit the column width, the width winds up as 43.00. So, as long as the computed width exceeds 43.00, the spreadsheet will show the full cell. With the new calculation, the computed width is 55.2722, satisfying our condition. This is wider than expected, but that is generally true for this type of computation. For example, for 'abcdefghijklmnopqrstuvwxyz', the computed width (before and after this change) is 31.7065, but Excel auto-fit actually uses 24.73.

"Exact width calculation" works well for fonts that support CJK, even without this PR. Since none of the fonts included in Shared/Font support CJK, this requires the use of the Shared/Font::setTrueTypeFontPath and Shard/Font::setExtraFontArray methods.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary

Why this change is needed?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.

[oleibman]

I was wrong to suggest a problem with exact width calculation" - I thought the font I was using supported the CJK characters, but it doesn't - testing with a font with verified support for the characters worked just fine. Description has been updated.