pmb: Make RunOutputTypeDefault and RunOutputTypePopen enums

This allows us to get rid of some of the validation in sanity_checks()
as mypy handles this validation at "build time", and any typos in the
enum instantiation would be a runtime error rather than a silent
failure.

Additionally, it allows us to encode some of the behaviour of the
different output types into the type definition itself by using methods.

Part-of: https://gitlab.postmarketos.org/postmarketOS/pmbootstrap/-/merge_requests/2642

pmb/qemu/run.py

@@ -24,7 +24,7 @@ import pmb.chroot.initfs
 import pmb.config
 import pmb.config.pmaports
 import pmb.install.losetup
-from pmb.types import Env, PathString, PmbArgs
+from pmb.types import Env, PathString, PmbArgs, RunOutputTypeDefault
 import pmb.helpers.run
 import pmb.parse.cpuinfo
 from pmb.core import Chroot, ChrootType
@@ -470,7 +470,7 @@ def run(args: PmbArgs) -> None:
     process = None
     try:
         signal.signal(signal.SIGTERM, sigterm_handler)
-        process = pmb.helpers.run.user(qemu, output="tui", env=env)
+        process = pmb.helpers.run.user(qemu, output=RunOutputTypeDefault.TUI, env=env)
     except KeyboardInterrupt:
         # In addition to not showing a trace when pressing ^C, let user know
         # they can override this behavior: