Setter must replace embedded object instead of add a new object

[kneth]

What, How & Why?

When replacing an element in a list of embedded object, the existing object should be removed. Calling Obj::set_embedded() is replacing while Obj::insert_embedded() will create a new object and add it to the list without touching the existing element.

This closes #6239

☑️ ToDos

• 📝 Changelog entry
• 📝 Compatibility label is updated or copied from previous entry
• 📝 Update COMPATIBILITY.md
• 🚦 Tests
• 📦 Updated internal package version in consuming package.jsons (if updating internal packages)
• 📱 Check the React Native/other sample apps work if necessary
• 💥 Breaking label has been applied or is not necessary

[coveralls-official]

coverage: 86.24% (+0.05%) from 86.187%
when pulling ed2d271 on kneth/embedded-object-behavior
into cc63892 on main.

[elle-j]

Good and important fix!

[takameyer]

Wow, good fix!