Add workspace list filter by current run status

[arybolovlev]

Description

This PR adds a new filter option CurrentRunStatus to WorkspaceListOptions, allowing a list of Workspaces to be filtered by current run status.

Here is an example of listing workspaces with the current run status set to planned.

$ curl -s \
  --header "Authorization: Bearer $TFE_TOKEN" \
  --header "Content-Type: application/vnd.api+json" \
  --request GET \
"https://app.terraform.io/api/v2/organizations/XXX/workspaces?filter%5Bcurrent-run%5D%5Bstatus%5D=planned"

If this change is accepted, then I will raise a new PR to update the docs: https://developer.hashicorp.com/terraform/cloud-docs/api-docs/workspaces#query-parameters.

Testing plan

N/A.

External links

N/A.

Output from tests

Including output from tests may require access to a TFE instance. Ignore this section if you have no environment to test against.

$ TFE_ADDRESS="https://app.terraform.io/" TFE_TOKEN="X.atlasv1.X" go test ./... -v -run TestWorkspacesList
...
--- PASS: TestWorkspacesList (69.91s)
    --- PASS: TestWorkspacesList/without_list_options (0.21s)
    --- PASS: TestWorkspacesList/with_list_options (0.43s)
    --- PASS: TestWorkspacesList/when_sorting_by_workspace_names (0.34s)
    --- PASS: TestWorkspacesList/when_sorting_workspaces_on_current-run.created-at (26.03s)
    --- PASS: TestWorkspacesList/when_searching_a_known_workspace (0.20s)
    --- PASS: TestWorkspacesList/when_searching_using_a_tag (0.47s)
    --- PASS: TestWorkspacesList/when_searching_using_exclude-tags (0.73s)
    --- PASS: TestWorkspacesList/when_searching_an_unknown_workspace (0.17s)
    --- PASS: TestWorkspacesList/without_a_valid_organization (0.00s)
    --- PASS: TestWorkspacesList/with_organization_included (0.45s)
    --- PASS: TestWorkspacesList/with_current-state-version,current-run_included (18.81s)
    --- PASS: TestWorkspacesList/when_searching_a_known_substring (0.59s)
    --- PASS: TestWorkspacesList/when_wildcard_match_does_not_exist (0.57s)
    --- PASS: TestWorkspacesList/when_using_project_id_filter_and_project_contains_workspaces (1.12s)
    --- PASS: TestWorkspacesList/when_using_project_id_filter_but_project_contains_no_workspaces (0.46s)
    --- PASS: TestWorkspacesList/when_filter_workspaces_by_current_run_status (12.65s)
PASS
ok  	github.com/hashicorp/go-tfe	70.207s