Refactor get_indexes to return partition names and values

[damian3031]

Description

Resolves #476
get_indexes refactored to return list of dicts with partition name and partition values.
example output:

[
    {
        'partition_name': 'part_a',
        'partition_values': ['val1', 'val2', 'val3']
    },
    {
        'partition_name': 'part_b',
        'partition_values': ['val4', 'val5', 'val6']
    }
]

Non-technical explanation

Release notes

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* Fix some things. ({issue}`issuenumber`)