EnC: Implements support for generic type/method updates

[tmat]

Introduces the following capabilities that runtimes can now implement:

/// <summary>
/// Adding a static or instance method, property or event to an existing type (without backing fields), such that the method and/or the type are generic.
/// </summary>
GenericAddMethodToExistingType = 1 << 7,

/// <summary>
/// Updating an existing static or instance method, property or event (without backing fields) that is generic and/or contained in a generic type. 
/// </summary>
GenericUpdateMethod = 1 << 8,

/// <summary>
/// Adding a static or instance field to an existing generic type.
/// </summary>
GenericAddFieldToExistingType = 1 << 9,

Updates rude edit reporting accordingly.

Related: dotnet/runtime#85177

[tmat]

@davidwengier PTAL
@phil-allen-msft FYI