Add default values for track slots and initializer capacity

[amandalund]

This adds reasonable default values (based on our scaling studies) for num_track_slots and initializer_capacity in accel, celer-g4, and celer-sim. I've also added a default secondary_stack_factor in celer-sim and made that value consistent everywhere.

[github-actions[bot]]

Test summary

 4 400 files   6 735 suites   13m 36s :stopwatch:  1 807 tests  1 798 :white_check_mark:  9 :zzz: 0 :x: 23 030 runs  22 945 :white_check_mark: 85 :zzz: 0 :x:

Results for commit 5c4e51b5.

:recycle: This comment has been updated with latest results.

[esseivaju]

Since these are changes to accel, should we maybe have a class there that centralizes good default parameters, e.g.

struct DefaultOptions
{
    constexpr int stack_factor{8};
};

Then all downstream applications can set their input from there. You could even later add template parameters to specialize for the build options / system we're building on.

[amandalund]

Since these are changes to accel, should we maybe have a class there that centralizes good default parameters

Yeah, definitely good to have them all centralized. That should be where we're headed with the inp refactor: I think eventually we'll be removing the SetupOptions and the app inputs altogether and replacing them with the inp classes, which will be reused across the different front ends and should reduce duplication and improve consistency..