Add UI to choose if import "from IPFS" should be lazy or full

Right now MFS import "from IPFS" is done via `ipfs files cp` on CLI, `Import -> from IPFS` on Files screen in ipfs-webui, or by external tools like IPFS Companion.

In all cases, it is "lazy" so we don't fetch any new blocks. MFS protects blocks that are already in IPFS node cache, but to have full local copy one needs to add explicit local pin via "Set pinning" UI.

What we could improve here is to
- detect if imported path is fully available locally, and if not, give option to preload full copy (we could reuse "local pins" for facilitating this, or run `ipfs dag stat).
- I imagine this would happen in modal opened for `Import → From IPFS` – if some blocks are missing, we would show the total size, % and how much needs to be fetched to get full copy + a checkbox that would force preload
- add `#/import-content-path/ip[n|f]s/id/something` route that triggers `Import → From IPFS` UI on Files scrteen with pre-filled path
- this could then be integrated with IPFS Companion and other tools