Optimize formatTime utility (#3777)

Adds benchmarks and unit tests for the function

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

tests/CMakeLists.txt

@@ -18,6 +18,7 @@ set(test_SOURCES
     ${CMAKE_CURRENT_LIST_DIR}/src/IrcHelpers.cpp
     ${CMAKE_CURRENT_LIST_DIR}/src/TwitchPubSubClient.cpp
     ${CMAKE_CURRENT_LIST_DIR}/src/TwitchMessageBuilder.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/src/FormatTime.cpp
     # Add your new file above this line!
     )