change custom_types contract to be equivalent to the one in soroban-cli

[BlaineHeffron]

What

Changing custom_types contract to match the one in stellar-cli.

Why

This allows us to use soroban client init in the js-stellar-sdk instead of using prebuilt wasms. We needed functions to do tests on. I noticed that custom_types in this repo was identical to increment so I figured it was fine to change it.

Close stellar/js-stellar-sdk#980

Known limitations

N/A

[chadoh]

Thanks! I want to add that this will also allow us to use soroban contract init to set up tests in stellar-cli, rather than include its own modified versions of soroban-examples in the test-wasms folder.

[chadoh]

Note that a CI test for the custom_types contract is now failing

[BlaineHeffron]

formatting should be fixed now

[willemneal]

@BlaineHeffron @ElliotFriend @fnando, one Test is failing and I can't seem to have the permissions to re-run it.