API: Convert flag constants to [Flags] enums, where appropriate

[NightOwl888]

Much analysis must be done to ensure that the APIs contain all possible enums so all supported flags parameters can be passed, possibly by adding parameters for multiple enums.

This has already been done on the Normalizer class, but there are still other classes that use an int for flags which can accept a wide range of options. We don't necessarily need to make this any more than cosmetic - the values of the [Flags] enum values can remain the same as the constants that are being used now.