[AXON-46] Add remote auth flow using atlascode-backend

[sdzh-atlassian]

What is this?

The next PR in the chain to enable a smooth 3LO-from-anywhere experience in the extension ;)

With this, we can now use an external service to bounce authentication from - in this PR it's referred to as the JiraRemote OAuth strategy

Short recap of the changes:

• Fork the existing monolithic OAuth process, split it in 2 parts (start via user action / finish via deeplink)
• Add a button (completely invisible to everyone, FF pending) to trigger the new oauth
• Add an ability to configure OAuth client from the environment on the fly, for dev purposes
• Move OAuth strategy data into their own file, now with a bunch of docs
• Implement URIHandler path for /auth
• A whooooole lot of IPC/messaging boilerplate 😞

What's notably missing:

• OAuth attempt/session management
• The way to trigger new auth outside of dev environment is effectively hidden
• PKCE for the new Jira auth
• Bitbucket remote auth

There are also some known issues - for instance, the credentials seemingly get bundled between the strategies and somehow invalidate themselves - rather inconsistently, at that 😞

I'm leaving the follow-up to follow-up PRs. Also, some of the issues might be addressed by #79

How was this tested

• Unit tests, especially the new one on Strategy/StrategyData to prevent regressions
• E2E tested the new flow
• E2E tested the old flow

[cabella-dot]

overall looks good to me, just those 2 nits

[marcomura]

two minor comments, LTGM