Enable interceptors implicitly in binder gen nupkg when generator is enabled

[layomia]

• Fixes Update config binding gen nupkg transitive build target to use granular interceptor opt-in #91419. RC-2 candidate.
• Interceptors feature is required for source-gen to work; enable it implicitly using granular opt-in (i.e only for the namespace that we emit binding logic into)
• Corresponding web SDK change Move to granular opt-in for interceptors preview sdk#35024
• Not blocked on the new Roslyn version that contains the granular feature flowing into the SDK ([release/8.0.1xx] Update dependencies from dotnet/roslyn sdk#35018).

@dotnet/area-extensions-configuration @dotnet/area-infrastructure-libraries @captainsafia

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Issue Details

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Fixes #91419. RC-2 candidate.

@dotnet/area-extensions-configuration @dotnet/area-infrastructure-libraries @captainsafia

Author:	layomia
Assignees:	layomia
Labels:	area-Extensions-Configuration
Milestone:	8.0.0

[tarekgh]

LGTM.

Did we test this manually? Is there a way we can add a test for this? This shouldn't block this PR though.

[layomia]

Yes this was manually tested; like the previous change (#84379).

Unlike the SDK (e.g. in dotnet/sdk#35024), we don't seem to have a pattern for testing inbox/nupkg target changes.

@ViktorHofer do you have thoughts on possibilities here (for future/follow-up) ?

[layomia]

/backport to release/8.0

[github-actions]

Started backporting to release/8.0: /~https://github.com/dotnet/runtime/actions/runs/6077015411