Adds Protocol 20 (Soroban) support to the XDR and API.

[paulbellamy]

This is a holistic view on the upstream merge. Here are the changelog / release notes:

v10.0.0-beta.0: Protocol 20 Support

Breaking Changes

Node 16 is the new minimum version to use the SDKs.

Major XDR Changes

The XDR has been massively overhauled to support Soroban in Protocol 20, which means new operations, data structures, and a transaction format as well as new overlay features.

The core data structure of Soroban is a generic type called an ScVal (smart contract value, which is a union of types that can basically represent anything (numbers, strings, arrays, maps, contract bytecode, etc.). You should refer to the XDR for details, and you can rely some new APIs to make dealing with these complex values easier:

• nativeToScVal helps convert native types to their closes Soroban equivalent
• scValToNative helps find the closest native JavaScript type(s) corresponding to a smart contract value
• scValToBigInt helps convert numeric ScVals into native bigints
• ScInt and XdrLargeInt help convert to and from bigints to other types and form sized integer types for smart contract usage

The following are convenience methods for building out certain types of smart contract-related structures:

• buildInvocationTree and walkInvocationTree are both ways to visualize invocation calling trees better
• authorizeInvocation helps multiple parties sign invocation calling trees
• humanizeEvents helps make diagnostic events more readable

Added

The following are new APIs to deal with new Soroban constructs:

• Address, which helps manage "smart" addresses in the Soroban context. Addresses there (used for auth and identity purposes) can either be contracts (strkey C...) or accounts (strkey G...). This abstraction helps manage them and distinguish between them easily.
• Contract, which helps manage contract identifiers. The primary purpose is to build invocations of its methods via the generic call(...), but it also provides utilities for converting to an Address or calculating its minimum footprint for state expiration.
• Three new operations have been added related to Soroban transactions:
  • invokeHostFunction for calling contract code
  • bumpFootprintExpiration for extending the state lifetime of Soroban data
  • restoreFootprint for restoring expired, off-chain state back onto the ledger
• The TransactionBuilder now takes a sorobanData parameter (and has a corresponding .setSorobanData() builder method) which primarily describes the storage footprint of a Soroban (that is, which parts of the ledger state [in the form of xdr.LedgerKeys] it plans to read and write as part of the transaction).
  • To facilitate building this out, there's a new SorobanDataBuilder factory to set fields individually
• The TransactionBuilder now has a cloneFrom(tx, opts) constructor method to create an instance from an existing transaction, also allowing parameter overrides via opts.
• We've added a GHA to track bundle size changes as PRs are made. This protocol upgrade adds +25% to the final, minified bundle size which is significant but unavoidable given the size of the upgrade.

[paulbellamy]

Fixes stellar/js-stellar-sdk#787

[piyalbasu]

@paulbellamy Apologies, I accidentally published a new version of this branch while trying to debug an issue in Freighter. It just created a new version 8.2.2-soroban.8 that is exactly the same as soroban.7. NPM won't allow that version to be unpublished and reused, so the next version will need to be 8.2.2-soroban.9.

Again, sorry about that. The automated pipeline worked a bit too well, it seems 😬