clang-tidy: enable clang-tidy

Enable the first check: readability-identifier-naming

Also fixed all check failures.

Tested:
1. compiles, no clang-tidy failures
2. the two daemons work correctly on hardware regarding DBus APIs

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: Ic415e857726e8f521c1d61a3e7f0c85121c0d284
diff --git a/mainapp.cpp b/mainapp.cpp
index 9ae2ac4..d8258cc 100644
--- a/mainapp.cpp
+++ b/mainapp.cpp
@@ -20,14 +20,14 @@
 #include <string>
 
 // D-Bus root for user manager
-constexpr auto USER_MANAGER_ROOT = "/xyz/openbmc_project/user";
+constexpr auto userManagerRoot = "/xyz/openbmc_project/user";
 
 int main(int /*argc*/, char** /*argv*/)
 {
     auto bus = sdbusplus::bus::new_default();
-    sdbusplus::server::manager_t objManager(bus, USER_MANAGER_ROOT);
+    sdbusplus::server::manager_t objManager(bus, userManagerRoot);
 
-    phosphor::user::UserMgr userMgr(bus, USER_MANAGER_ROOT);
+    phosphor::user::UserMgr userMgr(bus, userManagerRoot);
 
     // Claim the bus now
     bus.request_name(USER_MANAGER_BUSNAME);