log: Make log_max_recent have an effect again.

The log improvements in a747aea
unfortunately left log_max_recent broken because m_max_recent wasn't
used anymore.

Eliminate m_max_recent and set the capacity of the m_recent ring buffer
when log_max_recent changes. In order to call set_capacity(),
ConcreteEntry needed its move constructor set noexcept.

I haven't followed the boost code all the way down but I suspect that
setting the ring buffer capacity to anything less than 1 entry will
probably cause problems, so restrict log_max_recent to >=1.

Also fix a wrong variable used for printing the max new entries during
"log dump".

Signed-off-by: Joshua Baergen <jbaergen@digitalocean.com>
(cherry picked from commit 3d59ba1)

Conflicts:
  - file: src/common/options/global.yaml.in
    desc: not exists in pacific?

src/log/Entry.h

@@ -90,7 +90,7 @@ class ConcreteEntry : public Entry {
     str.assign(strv.begin(), strv.end());
     return *this;
   }
-  ConcreteEntry(ConcreteEntry&& e) : Entry(e), str(std::move(e.str)) {}
+  ConcreteEntry(ConcreteEntry&& e) noexcept : Entry(e), str(std::move(e.str)) {}
   ConcreteEntry& operator=(ConcreteEntry&& e) {
     Entry::operator=(e);
     str = std::move(e.str);

src/log/Log.cc

@@ -132,7 +132,7 @@ void Log::set_max_new(std::size_t n)
 void Log::set_max_recent(std::size_t n)
 {
   std::scoped_lock lock(m_flush_mutex);
-  m_max_recent = n;
+  m_recent.set_capacity(n);
 }
 
 void Log::set_log_file(std::string_view fn)
@@ -490,8 +490,8 @@ void Log::dump_recent()
 			     tid_to_int(pthread_id), pthread_name), true);
   }
 
-  _log_message(fmt::format("  max_recent {:9}", m_max_recent), true);
-  _log_message(fmt::format("  max_new    {:9}", m_max_recent), true);
+  _log_message(fmt::format("  max_recent {:9}", m_recent.capacity()), true);
+  _log_message(fmt::format("  max_new    {:9}", m_max_new), true);
   _log_message(fmt::format("  log_file {}", m_log_file), true);
 
   _log_message("--- end dump of recent events ---", true);

src/log/Log.h

@@ -116,7 +116,6 @@ class Log : private Thread
   bool m_stop = false;
 
   std::size_t m_max_new = DEFAULT_MAX_NEW;
-  std::size_t m_max_recent = DEFAULT_MAX_RECENT;
 
   bool m_inject_segv = false;