Add make_addr function to MockApi

[DariuszDepta]

closes #1887

[DariuszDepta]

@chipshort @webmaster128

Default settings for Bech32 encoded addresses are:

• prefix: cosmwasm,
• variant: Bech32,
• input digest length: 32 B.

To have an option to change the default settings during MockApi instantiation, I would suggest adding a constructor named with_bech32, that will provide appropriate initialization values, like:

let mock_api = MockApi::with_bech32("juno", false, false);

where the definition could be like:

pub fn with_bech32(prefix: &'static str, bech32m: bool, short: bool) -> MockApi

where the arguments would be:

• prefix - any reference to static string,
• bech32m - true => Bech32m variant, false => Bech32 variant
• short - true => 20 bytes of input digest, false => 32 bytes of input digest

To make function addr_make with Bech32 address encoding more like opt-in, we could set the default prefix to an empty string, then this function would be an equivalent of Addr::unchecked:

let mock_api = MockApi::default();
let addr = mock_api.addr_make("creator");
assert_eq!(Addr::unchecked("creator"), addr);

but initializing MockApi with a non-empty prefix would create an address in Bech32 or Bech32m encoding:

let mock_api = MockApi::with_bech32("juno", false, false);
let addr = mock_api.addr_make("creator");
assert_eq!("juno1h34lmpywh4upnjdg90cjf4j70aee6z8qqfspugamjp42e4q28kqsksmtyp", addr.to_string());

This way we could preserve the old behaviour in existing tests, so users could gradually migrate from using Addr::unchecked to MockApi::addr_make without the need to change any logic or checks in tests.
Finally users could switch the MockApi initialization to generate Bech32 encoded addresses and gradually fix (if needed) existing tests. But this is just an idea to be considered before we complete this implementation.

[webmaster128]

Looks good overall. Few points inline

[webmaster128]

Great stuff. Just a few smaller things.

I'd appreciate if @chipshort could do another review and wrap this up for 1.5. We should have a CHANGELOG entry here.

[chipshort]

Looks good, just one small comment.

[chipshort]

LGTM