Support [IU]256, Timepoint, Duration (#1000)

### What

Support [IU]256, Timepoint, Duration. 

### Why

[TODO: Why this change is being made. Include any context required to
understand the why.]

### Known limitations

Author: jayz22

Cargo.lock

@@ -40,17 +40,17 @@ soroban-token-sdk = { version = "0.8.4", path = "soroban-token-sdk" }
 [workspace.dependencies.soroban-env-common]
 version = "0.0.16"
 git = "https://github.com/stellar/rs-soroban-env"
-rev = "422ce4110f26097e94835e0a70a4ed8c10b5bc16"
+rev = "7ed0c2903049092b70e6e4f366e70e677ce134ea"
 
 [workspace.dependencies.soroban-env-guest]
 version = "0.0.16"
 git = "https://github.com/stellar/rs-soroban-env"
-rev = "422ce4110f26097e94835e0a70a4ed8c10b5bc16"
+rev = "7ed0c2903049092b70e6e4f366e70e677ce134ea"
 
 [workspace.dependencies.soroban-env-host]
 version = "0.0.16"
 git = "https://github.com/stellar/rs-soroban-env"
-rev = "422ce4110f26097e94835e0a70a4ed8c10b5bc16"
+rev = "7ed0c2903049092b70e6e4f366e70e677ce134ea"
 
 [workspace.dependencies.stellar-strkey]
 version = "0.0.7"

Cargo.toml

@@ -755,7 +755,7 @@ pub use map::Map;
 pub use symbol::Symbol;
 pub use vec::Vec;
 mod num;
-pub use num::{I256, U256};
+pub use num::{Duration, Timepoint, I256, U256};
 mod string;
 pub use string::String;