Enable per-surface heatflux monitoring in history

[ChristianBauerEng]

Is your feature request related to a problem? Please describe.
In my application the heat flux over various surfaces is an important figure of merit of a specific design. Being able to monitor the average (or total) heat flux over different surfaces during runtime would be a good metric for judging convergence and quality of the design. Currently (as of 7.3.0) this does not seem to be possible.

A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
In my mesh I have defined various markers which indicate the surfaces of interest, where I would like the average heat-flux to evaluate over time. As suggested by the DryRun info I've indicated the surfaces with the MARKER_MONITORING specifier in the config file:

MARKER_MONITORING = (NS_WALL_RESONATORTIP, NS_WALL_RESONATOR3, NS_WALL_RESONATOR2)

However, the history and screen output shows only the heat flux aggregated over all surfaces.

Describe the solution you'd like
A clear and concise description of what you want to happen.

I would like the values of the HEAT group to behave just like those of the FLOW_COEFF group, where the heat flux is indicated on a per-surface basis. This would allow me to track the development of the heat fluxes with good time resolution, without having to write an excessive amount of surface files.

The output in the solution history could be similar to that of other output groups, i. e.:
"Avg_HeatFlux(SURF1)","Avg_HeatFlux(SURF2)",...

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.
Regularly exporting the entire surface data to discrete files and analyzing them during post-processing is a possible work-around, but leads to an excessive amount of files.

Additional context
Add any other context or screenshots about the feature request here.
My cases are highly transient and require quite some timesteps until a quasi-stationary limit cycle is reached. In the limit cycle the cycle-averaged net heat fluxes should be nearly zero. However, the magnitude of the heat transport is also of interest, which is why I would like to monitor these properties over time.

[pcarruscag]

Added in #1534