More work on the minimal-mode wasm build (now 603kb uncompressed). Remove the hard...

More work on the minimal-mode wasm build (now 603kb uncompressed). Remove the hard-coded feature-enable flags from sqlite3-wasm.c and rely on the build to provide them. Some wasm build cleanup, but attempts to completely overhaul it have been thwarted by my inability to make script-generated makefile code more legible/maintainable than the current eval spaghetti.

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