Write Integers With a Fraction Format As Excel Does

[ybai08]

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 is this change needed?

Fix #3625. With a fraction format, an integer was written as the integer alone. Excel writes a fraction in two cases, both noted in the issue:

Value	Format	Excel	PhpSpreadsheet before
1	0/0	1/1	1
1	??/???	1/1 (padded)	1
1	0 0/0	1 0/1	1
1	? ??/???	1 (padded)	1

So a format with no integer part always shows a fraction (N/1, or N*d/d with a fixed denominator d), and a format with an integer part shows N 0/1 when the last numerator placeholder is 0. With a ? or # numerator placeholder the fraction is left out, as before.

NumberFormatter replaced the # and 0 placeholders with ? before FractionFormatter saw the format, which lost the 0. That replacement now happens inside FractionFormatter (its only caller), after it notes whether the numerator ends in 0.

The 1/1, 1 0/1 and 1 results come from the issue thread. The other new cases (12/1, -3/1, 0/1 for 0 with 0/0, 500/100 for 5 with ??/100, 5 0/4 for 5 with 0 0/4) follow the same rule but have not been checked in Excel; Excel's padding with spaces is still not reproduced, as in the existing tests.

The suite was run:

• vendor/bin/phpunit tests/PhpSpreadsheetTests/Style/NumberFormatTest.php --filter testFormatValueWithMaskFraction: 8 of the 10 new cases fail without the change; all 37 pass with it.
• Full phpunit: 22445 tests, the same 1 error and 8 failures as on master (Html reader/writer, CODE of ℅, and the it_CH locale test, which depend on the local libxml/ICU/iconv).
• composer style (phpcs and php-cs-fixer), the PHPCompatibility check and bin/check-phpdoc-types.php: clean.
• phpstan: the same 5 $argv might not be defined reports in samples/Chart as on master, nothing new.
• Not run: composer versions on PHP versions other than 8.5, and Windows.