[Rust] Build against nightly Rust in CI

[asfimport]

In order to allow the parquet-rs code to be contributed, we need to move to using nightly Rust. We should build against both stable and nightly and allow failures against stable.

Reporter: Andy Grove / @andygrove
Assignee: Andy Grove / @andygrove

PRs and other links:

• GitHub Pull Request #3034

_{Note: This issue was originally created as ARROW-3868. Please see the migration documentation for further details.}

[asfimport]

Andy Grove / @andygrove:
Nightly and Stable Rust currently have different code formatting rules, so it is not possible to have both of them pass with the same code base.

[asfimport]

Chao Sun / @sunchao:
Can we skip the format check in stable? and I assume we had the same issue when using stable as default, is that right?

[asfimport]

Andy Grove / @andygrove:
Good idea. I just updated the PR to use separate scripts for stable vs nightly and only run the formatting checks for nightly.

[asfimport]

Andy Grove / @andygrove:
Issue resolved by pull request 3034
#3034