Remove the #define USE_CACHE since the formatters cache has been operational for a while now and has not caused issues that warrant disabling it
Also, print the cache hits statistics if the log is in debugging mode vs. LLDB being a debug build - this should make it easier to gather useful metrics on cache success rate for real users

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@184900 91177308-0d34-0410-b5e6-96231b3b80d8