GenAPI omits IndexerNameAttribute

[ericstj]

Describe the bug

When an indexer defines a custom name with IndexerNameAttribute GenAPI is not emitting that.

In the old GenAPI we had a special case for it:
https://github.com/dotnet/arcade/blob/e9a8e07465adf515a595e2afde2ffe893e973838/src/Microsoft.Cci.Extensions/Writers/CSharp/CSDeclarationWriter.Properties.cs#L39-L50

I have filed dotnet/roslyn#72007 to see if we want SyntaxGenerator to handle this, if not we'll need to workaround here.

To Reproduce

Run GenAPI against an assembly which uses IndexerNameAttribute, for example System.Xml.ReaderWriter
https://github.com/dotnet/runtime/blob/44b37e110c196aea18acbddfcc7a95b60b2a1c50/src/libraries/System.Xml.ReaderWriter/ref/System.Xml.ReaderWriter.cs#L617-L618

Observe missing attribute.