[Feature Request] `submitit` Multirun without sweeping

Feature Request

It would be nice to submit a set of jobs via a list without powersetting the params. For example:

python train.py -m --no-sweep param1=x,y param2=a,b

is equivalent to running

python train.py param1=x param2=a
python train.py -m param1=y param2=b

Motivation

Hydra's submitit launcher is super useful for submitting multirun jobs to a slurm cluster. However, the only use case supported currently is sweeps ie generating the cartesian product of all parameters. Yet sometimes we want to run multiple jobs with paired parameters for example

python train.py -m train_dataset=dataset1,dataset2 test_dataset=dataset3,dataset4. runid=train_1_test_3,train_2_test_4

but hydra will generate like 8 combinations.

Pitch

Describe the solution you'd like Instead, there should be a flag like --no-sweep that just basically does a for loop over the zip of the params and submits jobs for those. It can check that either only 1 parameter is listed or the lengths match