Flows: provide API to list flows from all datasets of the specified account

[zaychenko-sergei]

To support UI idea from kamu-data/kamu-web-ui#280, provide corresponding GraphQL API:

• it could start from Account query
• introduce something like AccountFlowRuns query
• then a method that is similar to DatasetFlowRuns::listFlows query, allowing filtering and pagination:

type DatasetFlowRuns {
        // ...
	listFlows(page: Int, perPage: Int, filters: DatasetFlowFilters): FlowConnection!
}

The view should be accessible to any user having a canView permission on the datasets. Note, if the observed account has some private datasets, to which the current user does not have any access, flows of those datasets should not be liste.

We also would need a mutation to pause/resume flows, similar to DatasetFlowConfigsMut::[pause|resume]Flows:

• introduce root Account mutation
• introduce AccountFlowConfigs mutation
• add operations pauseAccountDatasetFlows and resumeAccountDatasetFlows