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/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;