silx view: add a `search` helper

[payno]

goal

Sometimes files can contain a lot of information with 'tortuous' path. Users sometime (often) only remembers the name of a dataset or a part of name but not the full name. It could help to have a 'search' widget on the silx view application.

ideas on how it could be implemented

It could either filter groups / datasets containing this name and provide all items in another widget like in casual option 'search in all files'

Or like a casual 'search in file' with option to go to the next / previous item.

[payno]

Maybe we could first target HDF5 files. This way the source code might be reused in h5web. The visit function can be used https://docs.h5py.org/en/stable/high/group.html#h5py.Group.visit