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
(cherry picked from commit 7d2f055bcb)

pmb: Fix PmbArgs containing a string for output

While the annotations were changed to suggest that the output property
of PmbArgs contains a RunOutputType, at runtime it actually contained a
string because the argument parsing code hadn't been adapted to create a
RunOutputType. Fix this, and also change it to RunOutputTypeDefault as
while at it as that's more accurate.

Fixes 7d2f055bcb
Part-of: https://gitlab.postmarketos.org/postmarketOS/pmbootstrap/-/merge_requests/2644

pmb/helpers/lint.py

@@ -11,6 +11,7 @@ from pmb.core.pkgrepo import (
 from pmb.helpers import logging
 from pmb.helpers.exceptions import NonBugError
 from pmb.helpers.toml import load_toml_file
+from pmb.types import RunOutputTypeDefault
 import os
 
 import pmb.chroot
@@ -104,7 +105,7 @@ def check(pkgnames: Sequence[str]) -> None:
         if pmb.chroot.user(
             ["apkbuild-lint", *apkbuild_paths],
             check=False,
-            output="stdout",
+            output=RunOutputTypeDefault.STDOUT,
             working_dir=dest_paths[pkgrepo_name(repo)],
             env={"CUSTOM_VALID_OPTIONS": " ".join(get_custom_valid_options())},
         ):