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

test/lint/lint-format-strings.py

@@ -22,6 +22,7 @@ FUNCTION_NAMES_AND_NUMBER_OF_LEADING_ARGUMENTS = [
     'LogConnectFailure,1',
     'LogPrint,1',
     'LogPrintf,0',
+    'LogPrintfCategory,1',
     'LogPrintLevel,2',
     'printf,0',
     'snprintf,2',