Inconsistency with Decoupled and DecoupledIO

It's a source of confusion when to use Decoupled and when to use DecoupledIO -- can we just make them the same name and deprecate the inconsistent name?

**Type of issue**: feature request

**Impact**: API modification

**Development Phase**: request

**Other information**

**If the current behavior is a bug, please provide the steps to reproduce the problem:**

No bug
**What is the current behavior?**

You use `Decoupled` to create the thing but `DecoupledIO` is the type. This is really confusing.

**What is the expected behavior?**

They could both just be called `Decoupled`. And `DecoupledIO` would alias to Decoupled but pop up as deprecated.

**Please tell us about your environment:**

**What is the use case for changing the behavior?**

Less cognitive load

Locate the definitions and repository-wide usages of Decoupled and DecoupledIO, then review the public API and compatibility conventions. Done means the names are consistent, the old name is deprecated as requested, and the existing test suite passes without breaking current usage.

Written by the indexing model from the issue text.