macos: support configuration via CLI arguments

This makes it so `zig build run` can take arguments such as
`--config-default-files=false` or any other configuration. Previously,
it only accepted commands such as `+version`.

Incidentally, this also makes it so that the app in general can now take
configuration arguments via the CLI if it is launched as a new instance
via `open`. For example:

    open -n Ghostty.app --args --config-default-files=false

This previously didn't work. This is kind of cool.

To make this work, the libghostty C API was modified so that
initialization requires the CLI args, and there is a new C API to try to
execute an action if it was set.

macos/Sources/Ghostty/Ghostty.App.swift

@@ -45,12 +45,6 @@ extension Ghostty {
         }
 
         init() {
-            // Initialize ghostty global state. This happens once per process.
-            if ghostty_init() != GHOSTTY_SUCCESS {
-                logger.critical("ghostty_init failed, weird things may happen")
-                readiness = .error
-            }
-
             // Initialize the global configuration.
             self.config = Config()
             if self.config.config == nil {