refactor: rpi_boot: use chroot to run flash-kernel, ditch double rebo…

…ot strategy (#318)

This PR introduces one-step firmware install strategy to rpi_boot to deprecate the previously used double steps firmware update strategy. It also includes some internal refinements in rpi_boot.

* New features
1. support flash-kernel directly in post-update phase with chroot to standby slot.
2. now if system-boot partition is not mounted, rpi_boot will try to mount it.
3. rpi_boot now allows extra partitions after partition ID 3.

* Other changes
1. otaclient_common.linux: implement new subprocess_run_wrapper, which supports chroot.
2. otaclient.boot_control.common: implement a plain version of mount.

src/otaclient/app/boot_control/_common.py

@@ -32,6 +32,7 @@
     subprocess_check_output,
     write_str_to_file_sync,
 )
+from otaclient_common.typing import StrOrPath
 
 logger = logging.getLogger(__name__)
 
@@ -234,6 +235,36 @@ def set_ext4_fslabel(cls, dev: str, fslabel: str, *, raise_exception: bool = Tru
         cmd = ["e2label", dev, fslabel]
         subprocess_call(cmd, raise_exception=raise_exception)
 
+    @classmethod
+    def mount(
+        cls,
+        target: StrOrPath,
+        mount_point: StrOrPath,
+        *,
+        options: list[str] | None = None,
+        params: list[str] | None = None,
+        raise_exception: bool = True,
+    ) -> None:
+        """Thin wrapper to call mount using subprocess.
+
+        This will call the following:
+            mount [-o <option1>,[<option2>[,...]] [<param1> [<param2>[...]]] <target> <mount_point>
+
+        Args:
+            target (StrOrPath): The target device to mount.
+            mount_point (StrOrPath): The mount point to mount to.
+            options (list[str] | None, optional): A list of options, append after -o. Defaults to None.
+            params (list[str] | None, optional): A list of params. Defaults to None.
+            raise_exception (bool, optional): Whether to raise exception on failed call. Defaults to True.
+        """
+        cmd = ["mount"]
+        if options:
+            cmd.extend(["-o", ",".join(options)])
+        if params:
+            cmd.extend(params)
+        cmd = [*cmd, str(target), str(mount_point)]
+        subprocess_call(cmd, raise_exception=raise_exception)
+
     @classmethod
     def mount_rw(
         cls, target: str, mount_point: Path | str, *, raise_exception: bool = True