mem: add CacheVerbose debug flag, filter noisy DPRINTFs

Some of the DPRINTFs added to the classic cache in cset 45df88079f04,
while useful to those unfamiliar with the cache code, end up being
noise when you're familiar with the code but are trying to debug tricky
protocol issues.  (Particularly getting two messages from each cache
as it receives a snoop request then declares that there was no match.)

This patch introduces a CacheVerbose debug flag, and moves a subset of
the added DPRINTFs into that category, so that Cache by itself returns
to being a more succinct summary of cache activity.

Also added a CacheAll compound flag to turn on all the cache-related
debug flags (other than CacheTags, which you *really* have to want badly
to turn it on, IMO).

src/mem/cache/SConscript

@@ -42,4 +42,12 @@ DebugFlag('Cache')
 DebugFlag('CachePort')
 DebugFlag('CacheRepl')
 DebugFlag('CacheTags')
+DebugFlag('CacheVerbose')
 DebugFlag('HWPrefetch')
+
+# CacheTags is so outrageously verbose, printing the cache's entire tag
+# array on each timing access, that you should probably have to ask for
+# it explicitly even above and beyond CacheAll.
+CompoundFlag('CacheAll', ['Cache', 'CachePort', 'CacheRepl', 'CacheVerbose',
+                          'HWPrefetch'])
+