Auto merge of #19007 - MortimerGoro:const_codegen, r=emilio

Fix Const IDL value compilation errors in codegen

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I found that some const WebIDL values fail at rust compile time.

Example:

const long long TIMEOUT_IGNORED  = -1;

```
906 |     ConstantSpec { name: b"TIMEOUT_IGNORED\0", value: ConstantVal::DoubleVal(-1) }]
    |                                                                              ^^ expected f64, found integral variable
    |
    = note: expected type `f64`
               found type `{integer}`
```

I added a explicit cast to to fix the problem in conversions that may fail to compile.

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