feat(storage) default storage pool for volume creation [WD-7675]

[mas-who]

Done

• When a user creates a new custom storage volume from the volumes list, and if they’ve filtered this list to only show volumes from one storage pool, the volume creation form will now set the storage pool to match the filter by default.

QA

1. Run the LXD-UI:
   • On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @lorumic or @edlerd for access.
   • With a local copy of this branch, run as described here.
2. Perform the following QA steps:
   • Go to Storage -> Volumes tab. In the search and filter input box, filter volumes by a single storage pool. Then try create a volume, the storage pool selection should be defaulted to the filtered storage pool.
   • Now try filter volumes by multiple storage pools. Then try create a volume, the storage pool selection should be defaulted to the default storage pool. Same behaviour should be observed if there are no storage pool filters for volumes.

[webteam-app]

Demo starting at https://lxd-ui-573.demos.haus

[edlerd]

QA and code looks good to me.

[edlerd]

Might want to get a design review from @piperdeck as he suggested the change originally.

[piperdeck]

Everything looks good!