[BUILD][CORE] Extract the logging system into a subproject.

[ethouris]

NOTE: Prematurely merged #2964; any fixes for ofmt.h should apply there.

Main changes:

1. Removed explicitly defined identifiers in the logger FAs. Identifiers are still in use, but they are autogenerated and available through the logger global variable method id(). FA symbols are no longer a generated part of srt.h.
2. String-based dispatching to the logger is now built in into the logger. Loggers are registering themselves in the map during the initialization time.
3. The logging subproject can be potentially used in other projects. This can be moved to another repository and to be pinned into SRT repository as submodule, as well as used independently in other projects.
4. The minimum utilities required for the logger to function have been moved to the logger sources. This can be partially controversial, but these things bring in dependencies of the logging system.
5. The namespace for the logger symbols and the name for the configuration object are customizable. Potentially the configuration object can be implemented as a global variable, but a singleton is a safe form in case of being a dependent object.

The loggers now work a little bit different than before, although most of the accessing method remains intact:

1. You can still refer to the logger through its ID using the configuration object.
2. You can dispatch the ID using the string-based name through the configuration object.
3. This ID can be used to switch on/off particular FA.
4. If you have a direct access to the global variable designating the logger, you can obtain its ID through id() method.

The following facilities have been moved into this project as dependency utilities, some of them placed in the hvu namespace:

1. The compat part, SysStrError (the error description for the last system error) and SysLocalTime (getting tm as local time).
2. The ThreadName facility, which allows to modify the thread name visible in the debugger, as well as used in the logs.
3. The "ofmt" facility, which provides better formatting facility for sequential printable arguments.