Upgrade XDR to the final, stable testnet version.

[Shaptic]

Closes #699.

XDR has been upgraded to the latest stable version (https://github.com/stellar/stellar-xdr/commit/6a620d160aab22609c982d54578ff6a63bfcdc01). This is mostly renames, but it includes the following relevant breaking changes:

• Operation.bumpFootprintExpiration is now extendFootprintTtl and its ledgersToExpire field is now named extendTo, but it serves the same purpose.
• xdr.ContractExecutable.contractExecutableToken is now contractExecutableStellarAsset
• xdr.SorobanTransactionData.refundableFee is now resourceFee
• In turn, SorobanDataBuilder.setRefundableFee is now setResourceFee
• This new fee encompasses the entirety of the Soroban-related resource fees. Note that this is distinct from the "network-inclusion" fee that you would set on your transaction (i.e. TransactionBuilder(..., { fee: ... })).
• In TypeScript, the Operation.BumpFootprintExpiration is now Operation.ExtendFootprintTTL

Note: The diffs to src/generated/*.js and types/*.d.ts should be very readable.

[github-actions[bot]]

Size Change: -2.92 kB (0%)

Total Size: 3.16 MB

Filename	Size	Change
dist/stellar-base.js	2.31 MB	-2.06 kB (0%)
dist/stellar-base.min.js	842 kB	-859 B (0%)

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