[multi-radio] fix clang-tidy warnings (#6821)

- enable TREL in clang-tidy check
- add explicit keyword to constructors
- fix inconsistent parameter names
- remove redundant initializer
- use nullptr

script/make-pretty

@@ -115,6 +115,7 @@ readonly OT_CLANG_TIDY_BUILD_OPTS=(
     '-DOT_SNTP_CLIENT=ON'
     '-DOT_SRP_CLIENT=ON'
     '-DOT_THREAD_VERSION=1.2'
+    '-DOT_TREL=ON'
     '-DOT_COVERAGE=ON'
     '-DOT_LOG_LEVEL_DYNAMIC=ON'
     '-DOT_COMPILE_WARNING_AS_ERROR=ON'