Update wasmfs.make to get WASMFS building again, but changes made to OPFS-over-WASMFS...

Update wasmfs.make to get WASMFS building again, but changes made to OPFS-over-WASMFS since we last tested it have made it incompatible with how we used it. It can now only be used from worker threads, eliminating the one benefit it had over the sqlite3_vfs OPFS implementation. Remove/amend references to WASMFS in the docs and remove all WASMFS-specific test app links from index.html.

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