doc: More precise -debug and -debugexclude doc

I wondered how one could enable debug logging with `-debug=<category>` for multiple categories. Found out solution is to specify that option multiple times for each wanted category.

This PR documents this behavior and uses the same wording for the same behavior of `-debugexclude=<category>` to make that also clear and stringent.

Author: wodry

src/init.cpp

@@ -520,9 +520,9 @@ void SetupServerArgs(NodeContext& node)
     argsman.AddArg("-limitdescendantsize=<n>", strprintf("Do not accept transactions if any ancestor would have more than <n> kilobytes of in-mempool descendants (default: %u).", DEFAULT_DESCENDANT_SIZE_LIMIT), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-addrmantest", "Allows to test address relay on localhost", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-debug=<category>", "Output debugging information (default: -nodebug, supplying <category> is optional). "
-        "If <category> is not supplied or if <category> = 1, output all debugging information. <category> can be: " + LogInstance().LogCategoriesString() + ".",
+        "If <category> is not supplied or if <category> = 1, output all debugging information. <category> can be: " + LogInstance().LogCategoriesString() + ". This option can be specified multiple times to output multiple categories.",
         ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
-    argsman.AddArg("-debugexclude=<category>", strprintf("Exclude debugging information for a category. Can be used in conjunction with -debug=1 to output debug logs for all categories except one or more specified categories."), ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
+    argsman.AddArg("-debugexclude=<category>", strprintf("Exclude debugging information for a category. Can be used in conjunction with -debug=1 to output debug logs for all categories except the specified category. This option can be specified multiple times to exclude multiple categories."), ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-logips", strprintf("Include IP addresses in debug output (default: %u)", DEFAULT_LOGIPS), ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-logtimestamps", strprintf("Prepend debug output with timestamp (default: %u)", DEFAULT_LOGTIMESTAMPS), ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST);
 #ifdef HAVE_THREAD_LOCAL