Start Work: Set up a provider that manages the issue querying and includes caching and error handling

[sergeibbb]

This issue is a follow-up of #3621

Set up a provider that manages the issue querying and includes caching and error handling as we have with Launchpad. Most of this would be for future-proofing purposes - we don't automatically query for issues with this feature like we do for Launchpad - but the need for that may arise sooner than we think (for example - some UX on the Home view showing a count of how many issues we have, etc.) #3698 (review)

Perhaps we can do one of the following:

1. Create a startWorkProvider
2. Rename the launchpadProvider to be a bit more flexible outside the domain of Launchpad itself and extend it

And then we can add functions to the provider to:

1. Get searched issues, with caching and error handling like we do for Launchpad items, and the ability to filter out stale ones and other post-processing like we do with PRs for Launchpad (not that we have to implement any post-processing now, just the caching and error handling parts)
2. Complete actions on "start work" items, like creating a branch, etc.
3. Set up other utilities that we want in the future for Start Work so that the command file doesn't get out of hand.
4. Use those functions here as needed, like launchpad does with launchpadProvider. PR on Start Work operation in Home view (#3621) #3698 (comment)