"Cache" some of the data retrieved from Linear

[nir0s]

Some of the data we retrieve when e.g. creating issues shouldn't change that often. We should cache this data so that the user doesn't have to wait for Linear to return it. For example, every time an issue is created, we re-retrieve the available workflow states and assignees. Those probably don't change very often, so we may as well retrieve them just once, save them to the global context when any command that uses them first runs, and use them instead of re-retrieving.

For now, this can be done for:

• Workflow states
• List of assignees (team members)
• My teams
• Available priorities

[nir0s]

Btw, we can also add a command to force-update the cache, just in case.