Test: GitHub PR Extension - views location setting

[RMacfarlane]

Refs microsoft/vscode-pull-request-github#921

• anyOS @chrmarti
• anyOS @joaomoreno

Complexity: 2

Authors: @RMacfarlane, @rebornix

Please test against the nightly version of the extension, which should have the most recent changes:
marketplace.visualstudio.com/items?itemName=GitHub.vscode-pull-request-github-insiders

There's now a setting to control the location of the tree views of the extension. By default, a custom GitHub viewlet should be added with the trees. Test that the githubPullRequests.showInSCM setting can be used to toggle the views back to the SCM viewlet. When clicking on a link to a file from a diff on a PR description page, the file should be revealed in the tree.

Please file issues in this repo: Microsoft/vscode-pull-request-github

You can use auchenberg/pullrequest-demo for testing