Fix soroban test upgrades

[SirTyson]

Description

Resolves #4605

This test makes the following changes:

1. Refactors the root TestAccount to be managed by App
   • Prior to this change, there we frequently issues with sequence numbers. While there is only one actual root account, tests would periodically create multiple TestAccount objects for the one actual account. TestAccount caches the next sequence number, so this approach cause issues since one TestAccount root object would be out of sync with the others. This change makes it such that there is only one TestAccount object for the root.
2. modifySorobanNetworkConfig goes through full upgrade process
   • Previously, this function was very hacky and lead to testing bugs since we commited network config entries directly to the BucketList without going through the proper ledgerClose flow. Now, we actually go through the correct upgrade contract upload -> invoke -> arm -> externalize upgrade ledger flow.
   • Note that meta diffs have changed significantly, since each call to modifySorobanNetworkConfig now closes 4 ledgers. The root account also pays for these TXs, so balances have changed slightly as well.
3. Add support for ledgerMaxDependentTxClusters in upgrade related tests.

Checklist

• Reviewed the contributing document
• Rebased on top of master (no merge commits)
• Ran clang-format v8.0.0 (via make format or the Visual Studio extension)
• Compiles
• Ran all tests
• If change impacts performance, include supporting evidence per the performance document