Soroban: Add extendTtl Builtin Method

[tareknaser]

This PR adds support for extendPersistentTtl() method in Soroban, along with a test and documentation. Also, the Soroban testing infrastructure has been refactored to allow more flexible environment manipulation.

Documentation for extend_ttl
Fixes #1669

Changes

• Added support for extendPersistentTtl as a method on uint64 for the Soroban target.
  • In the Soroban SDK, extend_ttl is a generic function (IntoVal<Env, Val>)

pub fn extend_ttl<K>(&self, key: &K, threshold: u32, extend_to: u32)
where
    K: IntoVal<Env, Val>,

but Solidity does not support that, so it's implemented as a method instead.

• One assertion in the different_storage_types test is affected due to changes in diagnostic capture. A follow-up PR will address this.

[tareknaser]

Update: extendPersistentTtl is now renamed to extendTtl for both Persistent and Temporary storage types. For Instance storage type, a new builtin called extendInstanceTtl has been added as a standalone global function (not a method).

Tests for all storage types have been added in tests/soroban_testcases/ttl.rs.

[salaheldinsoliman]

Great!
Looks good but could you please:
1- Sign your commits for the DCO to pass
2- Add a test under integration/soroban?

[tareknaser]

1- Sign your commits for the DCO to pass

Sure, should be fixed now

2- Add a test under integration/soroban?

This is a bit tricky. Writing integration tests for the time-to-live functionality would require a way to access the current ledger state during tests (like we do now in tests/soroban_testcases/ttl.rs using soroban_sdk::testutils). We’d need to do something similar in JavaScript.

There’s a package @stellar/stellar-sdk that we currently use for Soroban integration tests, but I’m not sure if it has all the testing utilities we’d need. I haven’t looked into it deeply yet, but the general idea is that we’d have to update the testing setup to make it work (if possible).

For now, I’d like to get this PR through, and in a follow-up PR, I’ll add support for other variable types in extendTtl() method with tests for each type and explore adding integration tests.