[Rust] Use stable rust for no default test, clean up CI tests

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1. Rationale

   1. As @jorgecarleitao noted on ARROW-12204: [Rust][CI] Reduce size of Rust build artifacts in integration test #9889 (comment), we should be running the check if arrow compiles with stable rust as that is what we target for the arrow crate
   2. I noticed that there were several redundant settings of RUSTFLAGS
   3. The titles of many of the tests are confusing (to me) as they have a lot of detailed architecture / rust version information rather than the test title

Reporter: Andrew Lamb / @alamb
Assignee: Andrew Lamb / @alamb

PRs and other links:

• GitHub Pull Request #9904

_{Note: This issue was originally created as ARROW-12224. Please see the migration documentation for further details.}

[asfimport]

Andrew Lamb / @alamb:
Issue resolved by pull request 9904
#9904