[hat] Enable padding in the codegen as an option for the iFace types and Schemas

[jjfumero]

This PR extends the C99 code generator to allow the generation of padding if this option is specified in the Hat Data Type Schema.

For instance:

Schema<F32Array> schema = Schema.of(F32Array.class, f32Array->f32Array
            .arrayLen("length").pad(12).array("array"));

Generates this C99 struct:

typedef struct F32Array_s{
    int length;
    char pad$ZArmN[12];   // pad$ + 5 random letter to avoid accidental collision with other members of the buffer type
    float array[1];
}F32Array_t;

This change is required to enable efficient local memory: See #531

---

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[jjfumero]

/integrate

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[openjdk]

@jjfumero This change now passes all automated pre-integration checks.

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[hat] Enable padding in the codegen as an option for the iFace types and Schemas

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[openjdk]

@jjfumero
Your change (at version a1fc95a) is now ready to be sponsored by a Committer.

[mlbridge]

Webrevs

• 00: Full (a1fc95af)

[grfrost]

/integrate

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@grfrost Only the author (@jjfumero) is allowed to issue the integrate command. As this pull request is ready to be sponsored, and you are an eligible sponsor, did you mean to issue the /sponsor command?

[grfrost]

/sponsor

[openjdk]

Going to push as commit cad3fdf.

[openjdk]

@grfrost @jjfumero Pushed as commit cad3fdf.

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