Tidy up `FlagValueSource`

[bok-]

📒 Description

This PR makes a few changes to FlagValueSource and NonSendableFlagValueSource:

• Adds an explicit flagValueSourceID property instead of trying to piggy back off Identifiable.
• Renames name to flagValueSourceName to better disambiguate with other existing properties called name that a type you are trying to conform to FlagValueSource might have.
• Renames changes to flagValueChanges to better disambiguate with other existing properties called changes that a type you are trying to conform to FlagValueSource might have.

These changes resolve some errors building with Xcode 16 but are also just being a good citizen. We shouldn't be trying to force Identifiable on a type that just wants to be a FlagValueSource when all we need is an ID we can use for managing subscriptions.

This is part of the Vexil 3 alpha series.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud