Add input file SHA256 hash consts to Go/Rust generated code

[leighmcculloch]

What

Add input file SHA256 hash consts to Go/Rust generated code, injecting the following into the Stellar rs-stellar-xdr lib:

/// `XDR_FILES_SHA256` is a list of pairs of source files and their SHA256 hashes.
pub const XDR_FILES_SHA256: [(&str, &str); 6] = [
    (
        "xdr/curr/Stellar-SCP.x",
        "8f32b04d008f8bc33b8843d075e69837231a673691ee41d8b821ca229a6e802a",
    ),
    (
        "xdr/curr/Stellar-ledger-entries.x",
        "3aa135c309c2d67883f165961739b4940c90df59240d8aeef55deced8d7708b5",
    ),
    (
        "xdr/curr/Stellar-ledger.x",
        "ef746ead6bb8ef9541599796804d672f2994e2599a6dc595ece099e166b49f10",
    ),
    (
        "xdr/curr/Stellar-overlay.x",
        "8ecbc36d2a43103499a6416572c7cd7b4fd7638d1a2af515b81b463ce6909c51",
    ),
    (
        "xdr/curr/Stellar-transaction.x",
        "45fdeb428e68d6b07e3e3157b6404567e0efb712c9d4c90a61a1035854c32b90",
    ),
    (
        "xdr/curr/Stellar-types.x",
        "60b7588e573f5e5518766eb5e6b6ea42f0e53144663cbe557e485cceb6306c85",
    ),
];

Why

@graydon pointed out that in applications or systems like stellar-core that import multiple XDR generated libraries it is really easy to accidentally import libraries that were generated from different sources. This mistake has occurred once and could have reasonably significant consequences, so building in meta information that applications like stellar-core can validate seems worthwhile.

Close #88

Known Limitations

This change only adds them to the Go and Rust libs.

[graydon]

Yeah, we should do this -- I'm writing the core-side stuff presently.

[leighmcculloch]

TODO:

• Include the file name in the code, not just in the comment.

[leighmcculloch]

@graydon I've updated it to include the name of the file as you requested:

/// `XDR_FILES_SHA256` is a list of pairs of source files and their SHA256 hashes.
pub const XDR_FILES_SHA256: [(&str, &str); 6] = [
    (
        "xdr/curr/Stellar-SCP.x",
        "8f32b04d008f8bc33b8843d075e69837231a673691ee41d8b821ca229a6e802a",
    ),
    (
        "xdr/curr/Stellar-ledger-entries.x",
        "3aa135c309c2d67883f165961739b4940c90df59240d8aeef55deced8d7708b5",
    ),
    (
        "xdr/curr/Stellar-ledger.x",
        "ef746ead6bb8ef9541599796804d672f2994e2599a6dc595ece099e166b49f10",
    ),
    (
        "xdr/curr/Stellar-overlay.x",
        "8ecbc36d2a43103499a6416572c7cd7b4fd7638d1a2af515b81b463ce6909c51",
    ),
    (
        "xdr/curr/Stellar-transaction.x",
        "45fdeb428e68d6b07e3e3157b6404567e0efb712c9d4c90a61a1035854c32b90",
    ),
    (
        "xdr/curr/Stellar-types.x",
        "60b7588e573f5e5518766eb5e6b6ea42f0e53144663cbe557e485cceb6306c85",
    ),
];