Remove the #define USE_CACHE since the formatters cache has been operational...

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

llvm-svn: 184900