Merges the final Protocol 20 XDR (i.e. for testnet) into `soroban`

[Shaptic]

You can see that the XDR now points to the following:

• curr: https://github.com/stellar/stellar-xdr/commit/9ac02641139e6717924fdad716f6e958d0168491
• next: https://github.com/stellar/stellar-xdr/commit/440dc9512b6e72cf84965641c5eb495d6043ed73

As indicated here by @sisuresh. The following migrations needed to be made:

• src/xdr.js has been updated to import from curr_generated, flipping the switch from using next to curr
• other changes are described in 3b1eb163bcad70bd3246e0a7f2b357a5c9b3e8a4, replicated here:
• function invocation now needs an InvokeContractArgs structure
• signatureArgs was a 0-elem vec, now an ScVal w/ 0-elem vec
• bodyType and metaDataSizeBytes are gone
• some minor test stuff has been tweaked for readability

Note for reviewers: the diffs of src/next_generated.js and types/next.d.ts should actually be rather readable and a good way to see the underlying XDR schema changes in this bump.

[github-actions[bot]]

Size Change: -1.82 kB (0%)

Total Size: 3.13 MB

Filename	Size	Change
dist/stellar-base.js	2.29 MB	-1.51 kB (0%)
dist/stellar-base.min.js	833 kB	-304 B (0%)

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