cosmwasm_std: use BTreeMap in testing mocks

[mina86]

Avoid dependency on std in testing module by replacing usage of
HashMap by BTreeMap. The HashMap hasn’t been used in public API other
than DistributionQuerier::new method. While this breaks API, the
method hasn’t been included in stable cosmwasm-std release yet thus
the change is semver-compliant.

An alternative approach would be to change DistributionQuerier::new to
take iterator of pairs. It’d probably be somewhat cleaner even if
it’d cause some unnecessary allocations when constructing the object.

With this change it’s going to be possible to make cosmwasm-std
support no_std in entirely backwards-compatible way (even if someone
builds with no-default-features).

[mina86]

With this change it’s going to be possible to make cosmwasm-std support no_std in entirely backwards-compatible way (even if someone builds with no-default-features).

I haven’t fully verified this, but I’m fairly certain this is true. There will essentially be no need for std cargo feature¹ if testing module doesn’t use HashMap in public APIs. DistributionQuerier::new is the only offending interface and to be honest I think it should actually be changed into

    pub fn new<T>(withdraw_addresses: T) -> Self
    where
        T: core::iter::IntoIterator<Item = (String, String)>
    {
        /* ... */
    }

¹ Kind of. There’s still one test that will depend on std, but tests don’t influence API compatibility.

[chipshort]

Unfortunately, we already released 1.3 with the HashMap before seeing this PR, so this is a breaking change after all. However, 2.0 is planned, so we can do the change there.

I agree with the IntoIterator proposal.

[webmaster128]

I agree with the IntoIterator proposal.

@chipshort could you open a ticket for that for 2.0?