Move sqlite3-api-cleanup.js into post-js-footer.js to remove the final direct Emscrip...

Move sqlite3-api-cleanup.js into post-js-footer.js to remove the final direct Emscripten dependency from the intermediary build product sqlite3-api.js (the whole library, waiting to be bootstrapped). This is partly in response to [forum:4b7d45433731d2e0|forum post 4b7d45433731d2e0], which demonstrates a potential use case for a standalone sqlite3-api.js. This is a build/doc change, not a functional one.

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