Update release verification script to try and publish `cache` crate not `core` crate

[andygrove]

Which issue does this PR close?

N/A

Rationale for this change

0.12.0-rc2 release verification failed because we try and dry-run publish the core crate, but this now depends on the cache crate

What changes are included in this PR?

• Try and dry-run publish cache crate in release verification script
• Fill out Cargo metadata for cache crate

Are there any user-facing changes?