investigate why import is taking a while!

inspired by noting a delayed import in @jjnesbit's
- https://github.com/dandi/dandi-cli/pull/1839/changes#diff-2fe358926b67bf5e55ea39d873932575efecdaf2c1cf1facace7aa0259cb4c1cR943

and apparently it is due to fscacher

```
❯ time python -c 'from dandi.support.digests import get_dandietag'
python -c 'from dandi.support.digests import get_dandietag' 1.79s user 0.04s system 614% cpu 0.297 total
❯ time python -c 'import fscacher'
python -c 'import fscacher' 1.71s user 0.03s system 1071% cpu 0.163 total
```
atm not comprehending why, although in dev tree uv env it is faster albeit a bit different version

```
❯ time python -c 'import fscacher'
python -c 'import fscacher' 0.07s user 0.02s system 99% cpu 0.086 total
```
although no relevant diffs IMHO from released 0.4.4 ... later

Start by reproducing the reported timings with `python -c 'import fscacher'` and `python -c 'from dandi.support.digests import get_dandietag'`, then compare the released 0.4.4 environment with the dev-tree uv environment. Trace the import path to determine why fscacher is slow; done means the cause is identified and the required follow-up is clear.

Written by the indexing model from the issue text.