Move enum remarks to summary (part 1)

[gewarren]

Contributes to #5220.

[ghost]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[opbld32]

Docs Build status updates of commit da3a2c7:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/Microsoft.Extensions.DependencyInjection/ServiceLifetime.xml	✅Succeeded	View
xml/Microsoft.Extensions.Logging.Console/LoggerColorBehavior.xml	✅Succeeded	View
xml/Mono.Security.Interface/HashAlgorithmType.xml	✅Succeeded	View
xml/System.Activities/ActivityInstanceState.xml	✅Succeeded	View
xml/System.Drawing.Imaging/EncoderParameterValueType.xml	✅Succeeded	View
xml/System.Formats.Cbor/CborReaderState.xml	✅Succeeded	View
xml/System.IO/MatchType.xml	✅Succeeded	View
xml/System.Net.Http/HttpVersionPolicy.xml	✅Succeeded	View
xml/System.Reflection.Metadata/MetadataStreamOptions.xml	✅Succeeded	View
xml/System.Reflection.Metadata/SignatureAttributes.xml	✅Succeeded	View
xml/System.Reflection.Metadata/SignatureTypeCode.xml	✅Succeeded	View
xml/System.Reflection.PortableExecutable/DebugDirectoryEntryType.xml	✅Succeeded	View
xml/System.Reflection.PortableExecutable/PEStreamOptions.xml	✅Succeeded	View
xml/System.Reflection/AssemblyHashAlgorithm.xml	✅Succeeded	View

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[BillWagner]

This LGTM @gewarren

You can when ready.