wasm: lots of doc additions and refactoring. Refactored the WASM memory heap usage...

wasm: lots of doc additions and refactoring. Refactored the WASM memory heap usage to hopefully eventually account for a runtime-growable heap. Differentiate between supported TypedArray types for input SQL strings vs binding/fetching blobs. Might (untested) have implemented the ability to bind UtfNNArray values as blobs, where NN is one of 16 or 32.

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