Collect more information in the scanner

[ronaldoussoren]

The scanner should extract more information for a number use cases:

• availability information, in particular deprecation information
• collect the names of enum types, and associate that with enum labels and values (both for C enums and string enums)
• collect nullable info
• collect the type name for parameters/return values that have "@" as their encoded type
• collect "NS_UNAVAILABLE" attribute
• collect if enums are equivalent to IntEnum or IntFlag
• collect NS_STRING_ENUM and NS_EXTENSIBLE_STRING_ENUM information
• collect availability for aliases

This information can be used to:

• Generate documentation for the framework wrappers
• Add more detail to the framework wrappers
• Generate MyPy typing stubs

[ronaldoussoren]

Most of this is now implemented.

There is an attempt to collect type names, but that code is not quite right.