[Test Explorer] multiroot-workspace related issues

[connectdotz]

Issue Type: Bug

1. the TestController displayed id instead of label in the explorer
2. the test coverage did not display the overall (all workspaces) nor updated when the "active" workspace controller is changed
3. not sure if this is intended, but how should we run the coverage profile?

VS Code version: Code - Insiders 1.59.0-insider (Universal) (955a1ac, 2021-07-26T05:12:43.446Z)
OS version: Darwin x64 20.6.0
Restricted Mode: No

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-8700B CPU @ 3.20GHz (12 x 3200)
GPU Status	2d_canvas: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	3, 4, 3
Memory (System)	32.00GB (2.79GB free)
Process Argv	--enable-proposed-api Orta.vscode-jest --crash-reporter-id bb07f68d-9e6c-4982-a12f-528f81d06cb6
Screen Reader	no
VM	0%

[connor4312]

(1) was just fixed in 472a308. Test coverage is still a WIP, tracking under #123713.

[JacksonKearl]

Steps please :)

[connor4312]

1. Use the test provider sample https://github.com/microsoft/vscode-extension-samples/tree/main/test-provider-sample
2. Create a second controller and ctrl.items.add at least one test
3. In the Test Explorer tree view, verify that you see both controllers with their correct labels