Rounding in NumberFormatter

[oleibman]

Fix #2385. NumberFormatter is using sprintf on a float, and is seeing inconsistent rounding as a result (it will also occasionally result in -0). Change to round the number before presenting it to sprintf.

This is:

- [x] a bugfix
- [ ] a new feature

Checklist:

• Changes are covered by unit tests
• 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
• Documentation is updated as necessary

Why this change is needed?

[nohn]

Tests that seem to provoke that strange rounding behaviour are in https://github.com/nohn/PhpSpreadsheet/tree/strange_rounding_format_value_with_mask

Run with those tests failing: https://github.com/nohn/PhpSpreadsheet/actions/runs/1795815772