feat(vsts): Add Visual Studio extension

[dcramer]

Add basic VSTS integration using refactored components from JIRA, GitHub, and Asana. Also update LICENSES to be more correct. Currently it is limited to the 'Create Issue' action.

Fixes getsentry/sentry#5263

See also boylec/sentry-vsts#5

[dcramer]

Actually I'm going to implement OAuth before we do this

https://www.visualstudio.com/en-us/docs/integrate/get-started/authentication/oauth

[ghost]

	1 Error
🚫	Do not modify the License

	2 Warnings
⚠️	Changes to build requirements
⚠️	You should update CHANGES due to the size of this PR

Generated by 🚫 Danger

[dcramer]

getsentry/sentry#6124

[dcramer]

Would be great to follow up and add a basic repository provider. May not have webhooks, but we can always on-demand scrape commits when a release is created.

https://www.visualstudio.com/en-us/docs/integrate/api/git/overview

[dcramer]

Still some more cleanup, but in a good spot now.

• Uses OAuth for credentials (via linked changeset)
• Uses standard utilities for API calls and response handling

In the future we should:

• Add select of account/project to the create issue form
• Add 'Link Issue' action

[dcramer]

I also standardized a bunch of the redundant API client code, and we could probably re-use it for most if not all of the integrations to greatly trim down on semi-broken behavior.

[dcramer]

making a few more changes to future proof this

[dcramer]

• Removed fixed project
• Added link issue
• Future proofed things for on-premise installs, changing instance, etc

http://i.cra.mr/2V2X3L2t0I1E

[dcramer]

@macqueen ok rebased this though I will also do a review of the github changes now just in case i messed up something during the merge