Serialized decimal differs when set by script and editor slider

[beicause]

Tested versions

Reproducible in 4.5.beta6
Not reproducible in 4.4.1

Possible caused by:

• Use Grisu2 algorithm in String::num_scientific to fix serializing #98750

System information

Linux

Issue description

_20250822_114849.webm

Steps to reproduce

• Set float property to 0.1 in script, it's serialized as 0.1
• Set float property to 0.1 in editor slider, it's serialized as 0.09999999999126885

Minimal reproduction project (MRP)

editor-set-decimal.zip

[aaronfranke]

This is a pre-existing issue, but the lack of precision in the serialized number masked it from us, and PRs #98750 and #109100 changed the behavior, exposing this issue. I've opened PRs #109884 and #109887 to fix it.

[Calinou]

I can confirm this on 4.5.beta 3defc85 (Linux). This can potentially cause noise in VCS diffs when upgrading, so we should aim to fix this for 4.5 if possible.