vscode: Debug Variables View does not show multiple variables from Debug Adapter when names are not unique

Issue Type: Bug

When I provide a DAP Variables response from my debug adapter extension with the following content, reflecting multiple local vars named a, only one of them is shown in the Variables view.

{"variablesReference":1,"seq":11,"vars":[{"name":"<temporaries>","value":"<temporaries>","variablesReference":4},{"name":"a","value":"1","type":"number","variablesReference":0,"evaluateName":"a"},{"name":"a","value":"2","type":"number","variablesReference":0,"evaluateName":"a"},{"name":"a","value":"3","type":"number","variablesReference":0,"evaluateName":"a"},{"name":"a","value":"4","type":"number","variablesReference":0,"evaluateName":"a"}]}

VS Code version: Code - Insiders 1.50.0-insider (ddc98c3f620ab1d2ecad5942ebf4736060403d67, 2020-09-25T05:35:02.163Z) OS version: Windows_NT x64 10.0.18363

System Info

Item	Value
CPUs	Intel® Core™ i7-6850K CPU @ 3.60GHz (12 x 3598)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: enabled_on protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	63.91GB (27.54GB free)
Process Argv	–crash-reporter-id 1d78045f-7d02-46d4-981d-e8dc1b7d9885
Screen Reader	no
VM	0%

Extensions (10)

Extension	Author (truncated)	Version
bracket-pair-colorizer-2	Coe	0.2.0
vscode-eslint	dba	2.1.8
gitlens	eam	10.2.2
vscode-pull-request-github	Git	0.20.0
git-graph	mhu	1.26.0
remote-wsl	ms-	0.44.5
indent-rainbow	ode	7.4.0
vscode-zipexplorer	sle	0.3.1
lua	sum	0.20.8
factorio-lua-api-autocomplete	svi	0.7.0