Focus is repeatedly stolen from terminal

Reposted from https://github.com/microsoft/vscode/issues/125800

Issue Type: Bug

1. Open dotnet/winforms project
2. Click on the terminal tab
3. Repeat step 2

https://user-images.githubusercontent.com/2119212/121288205-fd09a880-c8b0-11eb-848b-7cc668a30f70.mov

VS Code version: Code 1.56.2 (054a9295330880ed74ceaedda236253b4f39a335, 2021-05-12T17:44:30.902Z)
OS version: Darwin x64 19.6.0

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz (8 x 2500)|
|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, 3, 3|
|Memory (System)|16.00GB (0.71GB free)|
|Process Argv|--crash-reporter-id 1fc67ee2-0174-4598-9f98-4537df0dd32c|
|Screen Reader|no|
|VM|0%|
Extensions (55)

Extension|Author (truncated)|Version
---|---|---
vscode-bazel|Baz|0.4.1
LinkCheckMD|bla|0.3.1
open-in-macdown|Cod|1.0.0
vscode-zonefile|Com|0.0.4
vscode-markdownlint|Dav|0.42.0
jshint|dba|0.11.0
vscode-eslint|dba|2.1.20
dhall-lang|dha|0.0.4
docs-article-templates|doc|0.2.11
docs-authoring-pack|doc|0.1.13
docs-images|doc|0.0.9
docs-linting|doc|0.0.7
docs-markdown|doc|0.2.94
docs-metadata|doc|1.0.6
docs-preview|doc|0.3.57
docs-scaffolding|doc|0.0.8
docs-yaml|doc|0.2.6
EditorConfig|Edi|0.16.4
prettier-vscode|esb|6.4.0
go|gol|0.25.1
terraform|has|2.12.0
haskell|has|1.4.0
hive-sql|jos|0.0.4
language-haskell|jus|3.4.0
vscode-sbt-scala|lig|0.2.4
autoconf|mae|0.1.0
hg|mrc|1.7.1
vscode-docker|ms-|1.13.0
csharp|ms-|1.23.12
vscode-kubernetes-tools|ms-|1.3.3
vscode-postgresql|ms-|0.3.0
python|ms-|2021.5.842923320
vscode-pylance|ms-|2021.6.0
jupyter|ms-|2021.6.832593372
cmake-tools|ms-|1.7.3
cpptools|ms-|1.4.1
powershell|ms-|2021.5.1
vscode-typescript-tslint-plugin|ms-|1.3.3
fabric8-analytics|red|0.3.3
java|red|0.79.2
vscode-commons|red|0.0.6
vscode-xml|red|0.16.1
vscode-yaml|red|0.19.2
preview-vscode|sea|2.2.5
code-spell-checker|str|1.10.2
html-preview-vscode|tht|0.2.5
simple-rst|tro|1.0.1
cmake|twx|0.0.17
vscodeintellicode|Vis|1.2.14
vscode-java-debug|vsc|0.34.0
vscode-java-dependency|vsc|0.18.4
vscode-java-pack|vsc|0.16.0
vscode-java-test|vsc|0.30.0
vscode-maven|vsc|0.31.0
markdown-all-in-one|yzh|3.4.0

A/B Experiments

```
vsliv368:30146709
vsreu685:30147344
python383cf:30185419
pythonvspyt602:30300191
vspor879:30202332
vspor708:30202333
vspor363:30204092
vswsl492:30256859
pythonvspyt639:30300192
pythontb:30283811
pythonvspyt551:30311712
vspre833:30267464
pythonptprofiler:30281270
vshan820:30294714
pythondataviewer:30285071
vscus158:30286553
pythonvsuse255cf:30311221
vscgsv2:30307504
vscorehov:30309549
vscod805cf:30301675
binariesv517:30312825

```

## Environment data
`dotnet --info` output:
VS Code version:
C# Extension version:

Host (useful for support):
Version: 5.0.6
Commit: 478b2f8c0e

.NET SDKs installed:
5.0.300 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 5.0.6 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 5.0.6 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
https://aka.ms/dotnet-download

## OmniSharp log

## Steps to reproduce
Open a clone of dotnet/winforms
Open a terminal tab
Try to use it

## Expected behavior
Focus should not be repeatedly stolen

## Actual behavior
Focus is repeatedly stolen.