Remove the Gradle `release` task

[toddjonker]

Our Gradle build logic defines a release task, largely a holdover from the Amazon build environment to appease my muscle memory.

The standard Gradle equivalent for "build production artifacts and test everything” is the build task, defined by Gradle's base plugin to depend on check and assemble:

Intended to build everything, including running all tests, producing the production artifacts and generating documentation.

I don't see a good reason to retain release.

This is straightford to fix in the build logic, but we should do a staged migration to ensure that we don't break any automation.