This serves two purposes:
1. It ensures that we call `get_or_create_table` to ensure that the embedder
already had a chance to create the given table (although this is mostly
redundant due to validation).
2. It allows the embedder to easily get the `ir::TableData` associated with this
table, and more easily emit whatever inline JIT code to translate the table
instruction (rather than falling back to VM calls).
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