Use table's index type when parsing element segments (#8380)

Resolves the spec test error in call_indirect64.wast:

```
run_command `/usr/local/google/home/stevenfont/code/binaryen3/bin/wasm-shell /usr/local/google/home/stevenfont/code/binaryen3/test/spec/testsuite/call_indirect64.wast` failed (1) 0 BUILDING MODULE [line: 3]
[wasm-validator error in module] i32 != i64: element segment offset must match table index type, on
(i32.const 0)
failed validation
```

Previously we always assumed a 32-bit index even if the table is 64
bits. Use the index type of the table during parsing.

Part of #8261.