Support encrypted mach-o files

[CouleeApps]

Some programs on macOS, such as Finder.app and Dock.app, are encrypted using a key found in the SMC. We should have a way to enter this key into binja and have it decrypt and analyze these binaries.

[psifertex]

Have an internal test build with the following feedback from early testing / review:

• popup / warning when user opens a file without the key set
• need to upstream botan changes
• possibly try to reload existing tab when setting is set (fall-back, make the setting itself suggest a "restart" which will restart/reopen when set)

[psifertex]

Bumping the impact to medium as there are now documented cases of malware now abusing this.