The addition of assert functions to Userland/js was done before we had load(..) implemented. Now that it exists, it seems like the right move the test helper functions to pure javascript instead of poluting js with random global functions.
By borrowing an "expect close" function from LibM/TestMath.cpp, we can make this a lot simpler. Also the parser now understands decimals!
Switch the LibJS test suite to use the native assert implementation surfaced inside the js repl when it's launched in test mode.
