[3.x] Log all types serialzied by fallback serializer once

[ReubenBond]

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Currently, it's difficult to know which types are being serialized using the fallback serializer (eg, BinaryFormatter or ILBasedSerializer), making it difficult to confidently migrate those types to their own serializers.

We should log each type which is serialized using the fallback serializer once, so that developers can search through logs to find them.

[ReubenBond]

We will add the following property to SerializationProviderOptions

/// <summary>
/// The <see cref="LogLevel"/> to use when logging types serialized by the <see cref="FallbackSerializationProvider"/>.
/// </summary>
/// <remarks>
/// The default value is <see cref="LogLevel.Information"/>.
/// </remarks>
public LogLevel FallbackSerializationLogLevel { get; set; } = LogLevel.Information;

[niblak]

@ReubenBond is there a PR for this already in progress? Happy to pitch in if not; it'd be good to get a more detailed breakdown of where the fallback provider is being used in our app.