treewide: adopt pathlib.Path and type hinting (MR 2252)

With the new chroot type, we can now write fancy paths in the pythonic
way. Convert most of the codebase over, as well as adding various other
type hints.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

pmb/helpers/args.py

@@ -1,11 +1,11 @@
 # Copyright 2023 Oliver Smith
 # SPDX-License-Identifier: GPL-3.0-or-later
 import copy
-import os
 from pathlib import Path
 import pmb.config
 from pmb.core.types import PmbArgs
 import pmb.helpers.git
+import pmb.helpers.args
 
 """This file constructs the args variable, which is passed to almost all
    functions in the pmbootstrap code base. Here's a listing of the kind of
@@ -75,7 +75,7 @@ def check_pmaports_path(args: PmbArgs):
     """
     if args.from_argparse.aports and not os.path.exists(args.aports):
         raise ValueError("pmaports path (specified with --aports) does"
-                         " not exist: " + args.aports)
+                        f" not exist: {args.aports}")
 
 
 def replace_placeholders(args: PmbArgs):
@@ -108,7 +108,7 @@ def add_deviceinfo(args: PmbArgs):
                          " <https://postmarketos.org/newarch>")
 
 
-def init(args: PmbArgs):
+def init(args: PmbArgs) -> PmbArgs:
     # Basic initialization
     fix_mirrors_postmarketos(args)
     pmb.config.merge_with_args(args)