More granular json-style and astyle

[kevingranade]

Summary

None

Purpose of change

Erk complainined that json-style (actually style-all-json, but whatever) is too slow, and he's right.

Describe the solution

Added idiomatic make rules for both astyle and style-json to enumerate the cpp/h and json files respectively as targets, and touch token files to cause make to ignore those files in the future unless they have been edited again.
This accomplishes two things. One, it instructs make to use whatever parallelism is authorized by the -j argument to run multiple instances of the linting commands. Two, it records timestampts so that when in a protracted edit cycle these targets won't waste time repeatedly re-checking files that have not changed since the last check.

Describe alternatives you've considered

Tons of options, this is pretty idiomatic and performant. Some kind of batching might be helpful to keep the system from executing these quite so many times, but if you throw -j 10 at it, it's already pretty fast.

Testing

Ran the commands, does a full re-test the first time through.
Ran commands with -j 10, with very, very noticeable improvement in speed.
Re-ran commands, observed instant completion with not files checked.
Edited some .json, .cpp and .h files and re-ran commands, only the edited files were re-checked and it was very fast.
Decent chance of this breaking on different platforms, so let the full test suite complete before merging.

Additional whatever

The -check and -all variants are untouched, there might be a good way to integrate them, but it seems complicated.
I double-checked that .gitignore does not need any new entries, as I stashed all the timestamp files under obj/ (or objwin/ on some systems? IDK if that even works).

[kevingranade]

Make is so weird sometimes, I had to declare a dependency on the json formatter exe from both the main target and the sub=target, because otherwise it will launch all the dependencies in parallel, which of course means it will try to simultaneously build the tool and execute it.