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/commands/log.py

@@ -3,7 +3,7 @@
 
 from __future__ import annotations
 from pmb import commands
-from pmb.types import PathString
+from pmb.types import PathString, RunOutputTypeDefault
 from pmb.helpers import run
 from pmb.core.context import get_context
 import pmb.config
@@ -38,4 +38,4 @@ class Log(commands.Command):
         # looks for an error / what's currently going on).
         cmd += [context.log]
 
-        run.user(cmd, output="tui")
+        run.user(cmd, output=RunOutputTypeDefault.TUI)