Handle offline/disconnected use cases gracefully

**Offline work**
There used to be a boolean option to "work offline" or otherwise ignore connection errors in the extension. This is helpful when working completely offline, or when a connection to the server is otherwise unavailable.

It looks like this feature was removed in [AXON-791-audit-and-remove-unused-settings](https://github.com/atlassian/atlascode/pull/699).

**Scenario**
My employer uses Bitbucket and Jira Datacenter editions, which are on-prem, and only accessible from our corporate VPN. Most often, I am not on our corporate VPN, unless and until I have to do something specific.

When I'm not on the VPN, the extension cannot reach our Jira server, and I see pop-up errors:
- There was an error connecting to `jira.school.edu`. Please log in again.
- Credentials refused for `jira.school.edu/rest`
- Something went wrong: Site previously failed authentication

... and then the extension removes my Jira PAT from the extension configuration, so even when I am online and able to reach the Jira server again, my token is gone, and I have to re-enter it into the extension config.

**Additional context**
Only the Jira portion of the extension errors out when it can't connect to the Jira server. The Bitbucket portion of the extension doesn't complain, retains my Bitbucket PAT, and automatically re-connects when it detects a valid connection to our Bitbucket server.

**Describe alternatives you've considered**
See above for the more graceful way the extension handles a failed Bitbucket connection. If bringing back an "offline option" is not feasible, maybe an alternative would be to have the Jira portion of the extension handle connection errors as the Bitbucket portion does.

Review PR 699, AXON-791, to understand the removed offline setting and compare how the Jira and Bitbucket portions handle failed connections. The work is done when Jira connection failures no longer produce the reported errors or remove the Jira PAT, and reconnection works when the server becomes reachable again.

Written by the indexing model from the issue text.