system: some refactoring

There's no need to move a temporary which is already an rvalue

Clean-up some redundant attributes and function in settings.
Make sure C types are proxied to fixed-sized ones, not the other way around.

Clean-up webprint implementation
- use typed duration for the backlog
- don't duplicate members and types for config, just re-use the struct as-is
- don't go over-the-top with const members, just proxy through a method

code/espurna/light.cpp

@@ -2408,7 +2408,7 @@ void _lightInitCommands() {
         }
 
         auto description = [&](size_t channel) {
-            ctx.output.printf("#%u (%s) input:%ld value:%ld target:%ld current:%s\n",
+            ctx.output.printf_P(PSTR("#%zu (%s) input:%ld value:%ld target:%ld current:%s\n"),
                     channel, _lightDesc(Channels, channel),
                     _light_channels[channel].inputValue,
                     _light_channels[channel].value,