STM seems to be late to the Z-party :).

Summary

• Added aliases to be consistent with the rest of library.
• Propagated aliases in ZSTM and STM.
• Removed partial as it was a bit misleading and used in a single test.
• Fixed some ZIO signatures.

Question

• Should we add missing alias companions (i.e. for *STM, *Managed etc.)? That might be a good first issue.