[MachO] Display type information for more load command types

[bdash]

This series of commits does the following:

1. Extracts the code that creates and applies types related to load commands into a shared location. It was previously duplicated across the Mach-O, shared cache, and kernel cache views.
2. Adds helpers for creating enums and structs. This reduces the amount of boilerplate that has to be skimmed when reading the type creation code for the various load commands and their related types.
3. Adds types for a number of load commands that were previously unhandled.
4. Improves the types on a number of existing load commands.