Update LogAcceptCategory() and unit tests with log severity levels

Co-authored-by: "Jon Atack <jon@atack.com>"

src/logging.cpp

@@ -124,6 +124,19 @@ bool BCLog::Logger::WillLogCategory(BCLog::LogFlags category) const
     return (m_categories.load(std::memory_order_relaxed) & category) != 0;
 }
 
+bool BCLog::Logger::WillLogCategoryLevel(BCLog::LogFlags category, BCLog::Level level) const
+{
+    // Log messages at Warning and Error level unconditionally, so that
+    // important troubleshooting information doesn't get lost.
+    if (level >= BCLog::Level::Warning) return true;
+
+    if (!WillLogCategory(category)) return false;
+
+    StdLockGuard scoped_lock(m_cs);
+    const auto it{m_category_log_levels.find(category)};
+    return level >= (it == m_category_log_levels.end() ? LogLevel() : it->second);
+}
+
 bool BCLog::Logger::DefaultShrinkDebugFile() const
 {
     return m_categories == BCLog::NONE;