Allow service key in Service attribute itself

[kzu]

This simplifies the API and reads much better than an unnecessary generic attribute which is rarer in C#.

We obsolete the older typed attribute since it's unnecessary now.

Update readme with docs on this and improve it too.

[devlooped-bot]

🧪 Details on Ubuntu 22.04.5 LTS

✅ Tests.CodeAnalysis.AddServicesAnalyzerTests.NoWarningIfAddServicesPresent
✅ Tests.CodeAnalysis.AddServicesAnalyzerTests.NoWarningIfNoServiceCollectionCalls
✅ Tests.CodeAnalysis.AddServicesAnalyzerTests.WarnIfAddServicesMissing
✅ Tests.CodeAnalysis.AddServicesAnalyzerTests.WarnIfAddServicesMissingMultipleLocations
✅ Tests.CodeAnalysis.ConventionAnalyzerTests.ErrorIfNonTypeOf
✅ Tests.CodeAnalysis.ConventionAnalyzerTests.NoErrorOnTypeOfAndLifetime
✅ Tests.CodeAnalysis.ConventionAnalyzerTests.WarnIfOpenGeneric
✅ Tests.ComponentModel.ComponentModelTests.Composition
✅ Tests.ComponentModel.ComponentModelTests.RegisterSingletonService
✅ Tests.ComponentModel.ComponentModelTests.RegisterTransientService
✅ Tests.ComponentModel.ComponentModelTests.ResolvesDependency
✅ Tests.Composition.CompositionTests.CompositionLifetimes
✅ Tests.Composition.CompositionTests.RegisterKeyedService
✅ Tests.Composition.CompositionTests.RegisterSingletonService
✅ Tests.Composition.CompositionTests.RegisterTransientService
✅ Tests.Composition.CompositionTests.ResolvesDependency
✅ Tests.DependencyInjection.ConventionsTests.RegisterGenericServices
✅ Tests.DependencyInjection.ConventionsTests.RegisterRepositoryServices
✅ Tests.DependencyInjection.ConventionsTests.RegisterServiceByRegex
✅ Tests.DependencyInjection.GenerationTests.RegisterInternalService
✅ Tests.DependencyInjection.GenerationTests.RegisterKeyedScopedService
✅ Tests.DependencyInjection.GenerationTests.RegisterKeyedSingletonService
✅ Tests.DependencyInjection.GenerationTests.RegisterKeyedTransientService
✅ Tests.DependencyInjection.GenerationTests.RegisterScopedService
✅ Tests.DependencyInjection.GenerationTests.RegisterSingletonService
✅ Tests.DependencyInjection.GenerationTests.RegisterTransientService
✅ Tests.DependencyInjection.GenerationTests.RegisterWithCustomServiceAttribute
✅ Tests.DependencyInjection.GenerationTests.RegisterWithGenericOutParameterHierarchy
✅ Tests.DependencyInjection.GenerationTests.ResolveMultipleKeys
✅ Tests.DependencyInjection.GenerationTests.ResolvesDependency
✅ Tests.DependencyInjection.GenerationTests.ResolvesKeyedDependency
✅ Tests.DependencyInjection.GenerationTests.ResolvesKeyedDependencyForNonKeyed
✅ Tests.DependencyInjection.GenerationTests.ResolvesKeyedFromContracts
✅ Tests.DependencyInjection.GenerationTests.ResolvesKeyedTransientDependency
✅ Tests.DependencyInjection.GenerationTests.RetrieveMany

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