fs.callbacks: simplify, ensure None does not break them, lazy richcallbacks

[skshetry]

Fixes #7704.

1. Simplifies implementation of callbacks, since only call() modifies the progress bars now. Progress bars now use the value/size from fsspec.Callback instead of using their own state.
2. Ensures that None value in relative_update/absolute_update does not break callbacks. This means that now we can guarantee that value will always be int. This is useful for filesystems that are not very compliant.
3. Gives the same treatment done in TqdmCallback: make it lazy #7715, makes rich callbacks lazy. Note that we don't use them anywhere yet.
4. Adds a test for that particular issue.

Note that size can be None, this has to be handled in respective callbacks, TqdmCallback now uses update_to which handles them, RichCallback also handles those well.