Clean up Cargo.toml files for tests

[jonjove]

What problem does your feature solve?

There are many inconsistencies and unnecessary lines in the Cargo.toml files for tests, such as #426 (comment).

What would you like to see?

Make them uniform and bring them in line with our current development guidelines.

What alternatives are there?

N/A

[leighmcculloch]

I recently went through the SDK repos Cargo.toml files and did this. Can you point me to the inconsistencies you see? The only one that stands out is the one mentioned in #426 (comment), but that's actually fine.

[jonjove]

Some of them depend on proptest (eg. add_i32) and some don't (eg. add_i64), but as far as I can tell none of them are actually using it. contract_data, linear_memory, vec don't specify publish = false but other tests do.

[leighmcculloch]

Thanks, adding this to the August iteration because the publish = false are likely to cause issues with releasing at the end of the iteration.

[leighmcculloch]

I removed prop_test recently from the sdk repo, and the publish thing got fixed I think at some point.