Code cleanup and minor optimizations

[Genbox]

Just a general code cleanup.

• A few spelling mistakes. Particularly in the help text.
• Removed unused namespaces
• Removed redundant code such as full type names and this/base reference
• Sorted modifiers such that they are consistent across
• Use Array.Empty instead of new[0]. This reduces the number of allocations.
• You don't have to use Environment.Exit() when you can just return. If you want to return an exit code, change Main() to return an integer and simply return the exit code.
• Changed all the string.Format() calls to use interpolation. The obvious benefit is readability, but another is that it uses the StringBuilderPool internally, thereby reducing allocations.

Each of these changes are in their own commits. None of the changes modify any logic, it is purely cleanup.

[Genbox]

FYI, I've made similar pull requests in upstream repositories (Rebeus, KrbRelay).