added functionality to distinguish between different leaderboards [closes #4047]

[ranjanmangla1]

This pr is to close issue : #4047

Earlier the leaderboard looked like this:

Now it looks like this:

Dropdown.Demo.mp4

I have changed how we get data of a particular challenge phase split. This is how data earlier it looked like:

[{"id":77,"dataset_split":39,"challenge_phase":39,"challenge_phase_name":"Denise Phase","dataset_split_name":"Split 39","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true},{"id":78,"dataset_split":40,"challenge_phase":39,"challenge_phase_name":"Denise Phase","dataset_split_name":"Split 40","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true}]
Phase Name: [{"id":79,"dataset_split":39,"challenge_phase":40,"challenge_phase_name":"Amanda Phase","dataset_split_name":"Split 39","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true},{"id":80,"dataset_split":40,"challenge_phase":40,"challenge_phase_name":"Amanda Phase","dataset_split_name":"Split 40","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true}]

Now it looks like this ( I am grouping data based on Phase ):

{"Denise Phase":[{"id":77,"dataset_split":39,"challenge_phase":39,"challenge_phase_name":"Denise Phase","dataset_split_name":"Split 39","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true},{"id":78,"dataset_split":40,"challenge_phase":39,"challenge_phase_name":"Denise Phase","dataset_split_name":"Split 40","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true}],"Amanda Phase":[{"id":79,"dataset_split":39,"challenge_phase":40,"challenge_phase_name":"Amanda Phase","dataset_split_name":"Split 39","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true},{"id":80,"dataset_split":40,"challenge_phase":40,"challenge_phase_name":"Amanda Phase","dataset_split_name":"Split 40","visibility":3,"show_leaderboard_by_latest_submission":false,"show_execution_time":false,"leaderboard_schema":{"labels":["score"],"default_order_by":"score"},"is_multi_metric_leaderboard":true}]}