components: Expanded aliases should be deduplicated

Currently this component:

```wasm
(component
(core module $m
(global (export "f") i32 i32.const 0)
)
(core instance $m (instantiate $m))
(core instance
(export "a" (global $m "f"))
(export "b" (global $m "f"))
)
)
```

dumps as:

```wasm
$ cargo run -q dump foo.wat
...
0x32 | 03 0b | core alias section
0x34 | 02 | 2 count
0x35 | 03 00 00 01 | core alias [global 0] InstanceExport { kind: Global, instance_index: 0, name: "f" }
| 66
0x3a | 03 00 00 01 | core alias [global 1] InstanceExport { kind: Global, instance_index: 0, name: "f" }
| 66
...
```

This should ideally only create one core alias annotation instead of two, recognizing that the alias was already added.