Use journal-gatewayd's new /boots endpoint to list boots (#5914)

* Use journal-gatewayd's new /boots endpoint to list boots

Current method we use for getting boots has several known downsides, for
example it can miss some incomplete boots and the performance might be
worse than what we could get by using Systemd directly. Systemd was
missing a method to get list boots through the journal-gatewayd but that
should be addressed by the new /boots endpoint added in [1] which
returns application/json-seq response containing all boots as reported
in `journalctl --list-boots`.

Implement Supervisor methods to parse this format and use the endpoint
at first, falling back to the old method if it fails.

[1] https://github.com/systemd/systemd/pull/37574

* Log info instead of warning when /boots is not present

Co-authored-by: Stefan Agner <stefan@agner.ch>

* Split records only by RS instead of LF in journal_boots_reader

* Strip only RS, json.loads is fine with whitespace

---------

Co-authored-by: Stefan Agner <stefan@agner.ch>

tests/conftest.py

@@ -47,6 +47,7 @@ from supervisor.coresys import CoreSys
 from supervisor.dbus.network import NetworkManager
 from supervisor.docker.manager import DockerAPI
 from supervisor.docker.monitor import DockerMonitor
+from supervisor.exceptions import HostLogError
 from supervisor.homeassistant.api import APIState
 from supervisor.host.logs import LogsControl
 from supervisor.os.manager import OSManager
@@ -463,6 +464,7 @@ async def journald_gateway() -> AsyncGenerator[MagicMock]:
             return (await client_response.content.read()).decode("utf-8")
 
         client_response.text = response_text
+        client_response.status = 200
 
         get.return_value.__aenter__.return_value = client_response
         get.return_value.__aenter__.return_value.__aenter__.return_value = (
@@ -471,6 +473,20 @@ async def journald_gateway() -> AsyncGenerator[MagicMock]:
         yield client_response
 
 
+@pytest.fixture
+async def without_journal_gatewayd_boots() -> AsyncGenerator[MagicMock]:
+    """Make method using /boots of systemd-journald-gateway fail."""
+
+    def raise_host_log_error_side_effect(*args, **kwargs):
+        raise HostLogError("Mocked error")
+
+    with patch(
+        "supervisor.host.logs.LogsControl._get_boot_ids_native"
+    ) as get_boot_ids_native:
+        get_boot_ids_native.side_effect = raise_host_log_error_side_effect
+        yield get_boot_ids_native
+
+
 @pytest.fixture
 async def journal_logs_reader() -> MagicMock:
     """Mock journal_logs_reader in host API."""