[M90-LTS] system_api: Add session_manager method to load shill profile

Add a session_manager DBus method which will be used to trigger loading
of a shill user profile.

BUG=b:183084821
TEST=none
Disallow-Recycled-Builds: all

Change-Id: I14b7974bac281bd52fbccddab9cab68c79e13fd7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2891561
Tested-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Pavol Marko <pmarko@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/3054090
Tested-by: Roger Felipe Zanoni da Silva <rzanoni@google.com>
Commit-Queue: Roger Felipe Zanoni da Silva <rzanoni@google.com>
Reviewed-by: Jana Grill <janagrill@google.com>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Owners-Override: Achuith Bhandarkar <achuith@chromium.org>
NOKEYCHECK=True
GitOrigin-RevId: 93dc3f11029906a4a19ec3bbf9b4eea7e06fd28c

dbus/login_manager/dbus-constants.h

diff --git a/dbus/login_manager/dbus-constants.h b/dbus/login_manager/dbus-constants.h
index 284e5ac..0a6d648 100644
--- a/dbus/login_manager/dbus-constants.h
+++ b/dbus/login_manager/dbus-constants.h
@@ -24,6 +24,7 @@
 const char kSessionManagerStartSession[] = "StartSession";
 const char kSessionManagerStopSession[] = "StopSession";
 const char kSessionManagerStopSessionWithReason[] = "StopSessionWithReason";
+const char kSessionManagerLoadShillProfile[] = "LoadShillProfile";
 const char kSessionManagerRestartJob[] = "RestartJob";
 const char kSessionManagerStorePolicyEx[] = "StorePolicyEx";
 const char kSessionManagerStoreUnsignedPolicyEx[] = "StoreUnsignedPolicyEx";