* Filestore: provide Filestore nodes
When strategy is set to "all" (the blockstore does all the providing when a
block is written), no providing was happening to Filestore blocks that were
not written to the underlying blockstore (so, the DAG leaves, as they live in
the filesystem directly). This fixes that.
* docs: clarify filestore and urlstore fix in changelog
both filestore (local file references) and urlstore (HTTP/HTTPS URL
references) blocks are now properly provided shortly after initial add
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