feat: allow admin to update unstaking duration for stake cw20

[vernonjohnson]

This PR allows the unstaking period to be changed in stake-cw20 and stake-cw20-gov. Addresses Issue #98

[JakeHartnell]

Looks great! Just needs some basic tests:

• Config can be updated
• Config can only be updated by admin

[vernonjohnson]

@JakeHartnell Tests are added

[ben2x4]

sorry, this sucks, but significant changes were made to the staking contract while this was in flight. Let me know if you have any issues/questions with resolving conflicts here.

[ben2x4]

Merge conflicts, might be a doozy

[vernonjohnson]

sorry, this sucks, but significant changes were made to the staking contract while this was in flight. Let me know if you have any issues/questions with resolving conflicts here.

No worries. Fixed the conflicts. Making one more change though: consolidating GetConfig and UnstakingDuration queries

[JakeHartnell]

Hmmmm, build errors, maybe we just delete Cargo.lock and re-build?

Will merge when fixed. Let's ship it.

[vernonjohnson]

Looks like the uint dependency is causing it to fail

Here's the output from the build pipeline:

error: edition 2021 is unstable and only available with -Z unstable-options.
Error: edition 2021 is unstable and only available with -Z unstable-options.
error: could not compile `uint`
Error: could not compile `uint`
To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
Warning: error: build failed
Error: The process '/home/runner/.cargo/bin/cargo' failed with exit code 101

[vernonjohnson]

One of our dependencies (uint) requires rust nightly. Updated the Github actions config to use the nightly toolchain

[ben2x4]

One of our dependencies (uint) requires rust nightly. Updated the Github actions config to use the nightly toolchain

why did this PR introduce this dependency?

[JakeHartnell]

One of our dependencies (uint) requires rust nightly. Updated the Github actions config to use the nightly toolchain

why did this PR introduce this dependency?

I think it's upstream in one of our deps. FWIW, also works in the latest stable release.