WritableAccount.add/subtract_lamports (#16750)

* add/sub lamports

* make add/sub return Result

* sample replacements

* cleanup

* fix up a few tests as examples

* move enum, cleanup, impl from

* fmt

* cleanup

* add lamports.rs

sdk/program/src/lamports.rs

@@ -0,0 +1,22 @@
+use crate::instruction::InstructionError;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum LamportsError {
+    /// arithmetic underflowed
+    #[error("Arithmetic underflowed")]
+    ArithmeticUnderflow,
+
+    /// arithmetic overflowed
+    #[error("Arithmetic overflowed")]
+    ArithmeticOverflow,
+}
+
+impl From<LamportsError> for InstructionError {
+    fn from(error: LamportsError) -> Self {
+        match error {
+            LamportsError::ArithmeticOverflow => InstructionError::ArithmeticOverflow,
+            LamportsError::ArithmeticUnderflow => InstructionError::ArithmeticOverflow,
+        }
+    }
+}

sdk/program/src/lib.rs

@@ -20,6 +20,7 @@ pub mod fee_calculator;
 pub mod hash;
 pub mod incinerator;
 pub mod instruction;
+pub mod lamports;
 pub mod loader_instruction;
 pub mod loader_upgradeable_instruction;
 pub mod log;