Auth next updates

[paulbellamy]

Fixes https://github.com/stellar/soroban-tools/issues/351

Depends on:

• [x] https://github.com/stellar/js-soroban-client/pull/47
• [x] https://github.com/esteblock/soroban-react/pull/21
• [ ] https://github.com/stellar/quickstart/pull/424

TODO

• [x] update rust deps
• [x] update soroban_token_spec.wasm from soroban-examples
• [x] check it all builds
• [x] fix rust tests
  • [x] https://github.com/stellar/rs-soroban-sdk/pull/856
• [x] stop doing approve & transfer workflow
  • [x] update the contract
  • [x] update the web app
  • [x] figure out how to build addresses in the web app
    • [x] add a helper for this to js-soroban-client
• [x] Check that sendTransaction is doing the prepareTransaction, auth and footprint updates
• [x] update soroban-client dep
• [x] update soroban-react deps
• [x] update quickstart image hash
• [ ] Test it all works