Clarify bundle adjust documentation of parameters used for each step of bundle adjust

[AndrewAnnex]

Is your feature request related to a problem? Please describe.
In https://stereopipeline.readthedocs.io/en/latest/tools/bundle_adjust.html and https://stereopipeline.readthedocs.io/en/latest/tools/parallel_bundle_adjust.html, I am often confused on which named bundle_adjust parameters are used for each processing step (0, 1, or 2) of parallel_bundle_adjust. Often that can be worked out by intuition though.

Describe the solution you'd like
I would like the documentation for bundle_adjust (or parallel_bundle_adjust, but since the parallel commands defer to the docs for bundle adjust that seems to be the more logical place) to include for each parameter an explicit description of which processing step that parameter is used for at the end of the sentence documenting the parameter.

For example for --num-iterations:

--num-iterations <integer (default: 1000)>
Set the maximum number of iterations. Used in processing step(s): 2.

Or something to this effect, if a parameter is used in multiple steps an enumeration like 0,1 would be fine. This doesn't need to be machine parsable, although that would be an interesting feature especially if the help/man page for the function in the terminal is also updated to include this information.

Some parameters partially describe their use in the processing steps, but it is inconsistent.

[oleg-alexandrov]

The bundle_adjust program has 110 parameters. It is not sustainable to specify for each parameter on what stage of processing it is used.

Maybe they could be grouped, by processing stage, but even here the need is not that high, I think. The reason parallel_bundle_adjust has three stages, is for convenience of parallelization, rather than some deep conceptual need.

If you are interested in producing subsections for these params, that may work. Note that some params are needed for all stages, like the output prefix. Those could be listed at the end, in a "shared" section.