JS: add a random element when assigning db IDs to Worker1 db instances. This addresse...

JS: add a random element when assigning db IDs to Worker1 db instances. This addresses [https://github.com/sqlite/sqlite-wasm/issues/113 | the npm project's ticket #113], which demonstrates that two independent workers can end up generating non-globally-unique IDs. That's not a bug, per se, but it makes the IDs useless for client-side mapping of db connection IDs to client-side state, so we add some randomness to them.

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