logging: add LogPrintfCategory to log unconditionally with category

prefixing the output with the passed category name.

- add documentation
- add a unit test
- update lint-logs.py
- update lint-format-strings.py

src/test/logging_tests.cpp

@@ -103,6 +103,7 @@ BOOST_FIXTURE_TEST_CASE(logging_LogPrintMacros, LogSetup)
     LogPrintLevel(BCLog::NET, BCLog::Level::Info, "foo8: %s\n", "bar8");
     LogPrintLevel(BCLog::NET, BCLog::Level::Warning, "foo9: %s\n", "bar9");
     LogPrintLevel(BCLog::NET, BCLog::Level::Error, "foo10: %s\n", "bar10");
+    LogPrintfCategory(BCLog::VALIDATION, "foo11: %s\n", "bar11");
     std::ifstream file{tmp_log_path};
     std::vector<std::string> log_lines;
     for (std::string log; std::getline(file, log);) {
@@ -114,7 +115,9 @@ BOOST_FIXTURE_TEST_CASE(logging_LogPrintMacros, LogSetup)
         "[net:debug] foo7: bar7",
         "[net:info] foo8: bar8",
         "[net:warning] foo9: bar9",
-        "[net:error] foo10: bar10"};
+        "[net:error] foo10: bar10",
+        "[validation] foo11: bar11",
+    };
     BOOST_CHECK_EQUAL_COLLECTIONS(log_lines.begin(), log_lines.end(), expected.begin(), expected.end());
 }