return all best partitions in case of tie

[GaspardR]

Is your feature request related to a problem? Please describe.
When jobs are submitted with the automatic selection from the partition config file, the partition with the greatest score for that job is used for submission. In case multiple partitions have the same score, only one is selected for submission. According to the slurm documentation, multiple partitions can be specified and the scheduler will use the one offering earliest initiation.
To me, this would could allow a better use of the available best partitions instead of restricting to only one.

Describe the solution you'd like
In case of a tie for partition selection, the function get_best_partition should return all of them instead of one.

Additional context
As an example, here's a partition file:

cpubase:
    max_mem_mb_per_cpu: 4000
    max_runtime: "1d"
    max_threads: 64
cpularge:
    max_mem_mb_per_cpu: 12000
    max_runtime: "1d"
    max_threads: 64