Implement task_group filtering for FedEval

[ishaileshpant]

• implement a new task_group filtering decorator 'with_selected_task_group' in Assigner class

• update all the sub-classes that use task_groups to use the decorator

• update fedeval sample workspace to use default assigner, tasks and aggregator

• use of federated-evaluation/aggregator.yaml for FedEval specific workspace example to use round_number as 1

• removed assigner and tasks yaml from defaults/federated-evaluation, superseded by default assigner/tasks

• added additional checks for assigner sub-classes that might not have task_groups

• Addressing review comments

• Updated existing test cases for Assigner sub-classes

• Remove hard-coded setting in assigner for torch_cnn_mnist ws, refer to default as in other Workspaces

• Use aggregator supplied --task_group to override the assinger selected_task_group

• update existing test cases of aggregator cli

• add test cases for the decorator

• rebased 25-Jan.1
  Signed-off-by: Shailesh Pant shailesh.pant@intel.com

• Testcases for task_group_filtering decorator

• Testing for all existing workspaces

• we shouldn't be saving any new models if running in evaluation mode.

• Change all workspaces to use new Assigner [Not needed as defaults ensure all workspace, by default use new assigner]

[teoparvanov]

Nice work, @ishaileshpant, I think it's looking good at this stage!
I just have a couple of minor remaining comments:

[rahulga1]

LGTM, just modify based on Teo's suggestions.

[psfoley]

Thanks for the PR, @ishaileshpant. The scenario of multiple user defined task groups needs to be considered before this can be approved. Details are provided in the comments. I can go into more depth on the Assigner design during our standup as well.

[ishaileshpant]

@kta-intel for the last task as discussed in #1258 i've created an issue #1321 and will track that fix via that